There has been much speculation and rumor that an Avenger will die in the upcoming movie, Avengers 2: Age of Ultron; it is important to note that this is still rumor and hasn't been confirmed. However, if an Avenger is indeed going to die in the upcoming film, it is likely that it will be none other than Black Widow.
As far as Avengers who could die, there are only three possibilities: Bruce Banner/The Hulk, Clint Barton/Hawkeye, and Natasha Romanoff/Black Widow. Tony Stark, Steve Rogers, and Thor have all been confirmed to appear in future installments in the Marvel Cinematic Universe (Captain America: Civil War and Thor: Ragnorak respectively).
Many feel the Clint Barton, a.k.a. Hawkeye, is the favorite to die in the upcoming Avengers 2. However, if the studios are looking to axe of a member of their flagship team, they are likely looking to cause a dramatic impact on the story and unfortunately, Hawkeye is the worst character to achieve that. To put it simply, he hasn't had a lot of screen time to be developed as a character for audiences, only appearing intermittently in Avengers and in a brief cameo in Thor.
It also has been confirmed that Hawkeye will get more screen time in Age of Ultron, which leads me to believe they are looking to increase his role in the MCU, not end it. Granted I will use this argument later for Black Widow's death; however, in the case of Hawkeye, his death would be more of a distraction than key plot point, and it wouldn't carry the same weight as say, Coulson's "death" in [The Avengers](movie:9040).
As for the The Hulk, the argument is quite simple, he is invincible. Alright, he is almost invincible; however, it would take time out of the main story in Avengers 2: Age of Ultron to introduce something from the comics that can kill the Hulk. While it is more likely to kill Bruce Banner, and many have pointed out how unwell he looks in the trailer, it is similarly just as hard to kill him, considering he has tried, as he states in the Avengers.
You can't I've tried ... I put a bullet in my head and the other guy spit it out!
Which leaves us with Black Widow as the most likely to die in Avengers 2. For one thing, unlike Hawkeye, she has appeared in numerous films and has been well developed as a fan favorite character. To kill Black Widow would achieve the shock that the studio might be trying to achieve. Now some might argue that she is save because she is the only lead female character and they need her to keep some diversity on the Avengers team, considering the Justice League is bringing Wonder Woman. However, this brings me to my next point, and that is that Black Widow is no longer the sole lead female superhero in the MCU.
In 2015, Marvel will be releasing not one, but two television shows in the MCU that will be lead by female characters. The first is Agent Carter, which will star Hayley Atwell as SSR Agent Peggy Carter. Taking place in the 1950s, it will follow Carter and the beginnings of SHIELD. Peggy Carter has been steadily gaining status as a lead character in the Marvel universe through appearances in the Marvel One-Shot Agent Carter, which the show is inspired from, as well as in Captain America: The Winter Soldier and Agents of Shield. She will also be appearing in [The Avengers: Age Of Ultron](movie:293035) and Ant-Man.
Also coming in 2015, following Marvel's Daredevil, is Jessica Jones portrayed by Krysten Ritter. She will be the first female superhero in the Marvel Universe to lead her own TV show. Jessica Jones will later tie in with [Daredevil](movie:47230), Iron Fist, and Luke Cage in the Defenders miniseries, a sort of street-level Avengers.
Also, Marvel's second season of Agents of SHIELD saw the introduction of not one but two female superheroes, Mockingbird, portrayed by Adrianne Palicki, and Quake/Daisy Johnson, Skye's Inhuman form as revealed in Agents of Shield episode "What They Become".
With all these new female superheroes, Black Widow will no longer be Marvel's only leading lady; and while she is still the only female character on the Avengers team right now, Marvel seems to have covered that as well. The Scarlet Witch, portrayed by Elizabeth Olsen, will be introduced in Avengers 2: Age of Ultron and, it is believed, will join the team alongside her brother Quicksilver, portrayed by Aaron Taylor-Johnson. In this way, Scarlet Witch will replace Black Widow as the female character on the team if Black Widow is killed.
With this sudden influx of female lead characters, the timing suggests that the studio is looking to find a leading female character to fill the gap that will be made when Black Widow is killed off in Avengers: Age of Ultron. As I've said before, Black Widow has had a lot of screen time which has helped solidify her place in the Marvel Universe as a fan favorite, it would be pretty hard to follow her up. However, the studio may feel that they can follow up Black Widow with at least one of these leading ladies to appease audiences.
While this may be a coincidence, and the increase in female characters doesn't have to do with [Black Widow](movie:1070824)'s death, there is still the question of Black Widow's future in the MCU. For one thing, many fans have clamored for her own solo film, and yet when executives revealed their Phase 3 lineup, Black Widow was noticeably absent. Considering that she is their leading lady, it seems strange that instead of her, they are handing lead TV shows to Peggy Carter and Jessica Jones and have even confirmed a Captain Marvel movie (a role I sincerely hope goes to Emily Blunt, Edge of Tomorrow anyone?).
Instead of her own film, Joss Whedon confirmed that there will have more focus on Black Widow and her story in the Avengers sequel.
“Natasha is a huge part of the sequel because you do want to concentrate on the people who don’t have their own franchises. Although [she's] in ‘Cap 2,’ [and] she’s great. She was the most fun for me because she’s not a hero, you know, and it’s something that I read—and I feel bad that I can’t remember who wrote the book—but it’s in one of the books explaining, ‘These guys are heroes, you are a spy. It’s a different thing—it’s a different skill set—and you don’t have their moral high ground or any of that good stuff.’ And that just makes her so interesting to me. So yeah, the stuff I’ve got going on with her in the second one is killer.”
Now why would they have more focus on Black Widow in Avengers 2 when they could have just had a standalone film for her. While a greater role for Hawkeye, as mentioned above, likely means he will live, with Black Widow it more likely means they are ending her story. This means they probably plan on killing her, and are just trying to answer some lingering questions and perhaps give her an epic sendoff.
Don't get me wrong, I am an immense fan of Black Widow and am not trying to wish for her death. I am just pointing out that the signs are there and pointing out the likely possibility. Out of all the Avengers that haven't been confirmed to survive Age of Ultron, her death would be the most impactful and tragic, which is what the studios would go for, similar to Agent Coulson. Also, they are anticipating that they are killing their only lead female superhero and are looking to introduce numerous female heroes next year to remedy that and possibly fill the gap left by her departure. Finally, most compelling is that her future is uncertain, no solo film and character focus in Avengers 2 Age of Ultron.
This is all circumstantial, thankfully, and might not mean anything (fingers-crossed). Still, if an Avenger will die in the upcoming movie, I think the most likely is Black Widow. If this is indeed the case, I would argue that the studio can still make it up to us. How? With an Agent Romanoff TV show, similar to Agent Carter. Just as Agent Carter is exploring the MCU in the 40s and 50s, a Black Widow TV show could explore the late 90s and early 2000s leading up to the events of Iron Man. One can only dream.