Marvel's popular television show, Agents of S.H.I.E.L.D.,
features a team of, surprisingly, S.H.I.E.L.D. agents. The two Marvel movies that have been released during the show's first season ([Thor: The Dark World](movie:206462) and Captain America: The Winter Soldier) both had impacts on the show; after The Dark World, the team went to London to clean up in the aftermath of Thor's battle and found themselves chasing after an Asguardian relic that gives humans the strength of gods. After The Winter Soldier, the team (obviously) had to deal with the collapse of S.H.I.E.L.D., an event that is still affecting them massively. But the real question is, when will the events in the show start to affect the movies? I have a few ideas:
The Ancient City
The ancient city (which is likely an abandoned Inhuman city; you can read my thoughts on it here) has been the main feature of [Agents of S.H.I.E.L.D.](series:722469) Season 2. There have been many, many references to both the Inhumans and the Kree (although most of said references have not been direct) and direct references to a weapon in a temple hidden in the city that can wipe out most of humanity. The locating of said weapon will most likely be the topic of Tuesday's fall finale of S.H.I.E.L.D. I don't find it likely that the weapon will be unleashed on the world, but I do think that, if Hydra gets their hands on it, the weapon could be part of an upcoming Marvel movie, possibly. Or maybe even the third season of S.H.I.E.L.D. if Hydra can't figure out how to use it or the Agents of S.H.I.E.L.D. don't retrieve it. Either way, the discovery of the weapon in the ancient city will have some affect on the MCU. Who knows, maybe it'll be a weapon that Ultron manages to get his hands on...
S.H.I.E.L.D. Directer Phil Coulson
After Hydra collapsed S.H.I.E.L.D. in the second Captain America movie, Nick Fury gave Coulson everything he needed to rebuild S.H.I.E.L.D. and told him to do so. Of course, Loki killed Coulson back in [The Avengers](movie:9040), and the fact that S.H.I.E.L.D. brought him back to life has been hidden from the Avengers so far. Introducing Coulson back to movies is bound to happen at some point and will create ripple in the pond of the MCU. When could this happen? My guess is either Ant-man or Captain America: Civil War.
I find Civil War to be the most likely of the two. Samuel Jackson a.k.a. Nick Fury, only has two more Marvel movies left on his contract after the new Avengers movie (unless the contract has been extended and I missed the news). There's the possibility of him being in Ant-Man, and I think that Fury will almost certainly be in the third Captain America movie. If Fury is in both, it's likely that he'll be killed in the Civil War movie as a way for him to leave the MCU. But even if Fury isn't in both and doesn't die, I think that Coulson will still return in the Civil War movie because with tensions brewing like that, S.H.I.E.L.D. will almost have to intervene and try and stop the oncoming war. If Coulson ends up in Ant-Man, I think it might be as an after-credit scene revealing himself to either Stark or Rodgers and telling them S.H.I.E.L.D. is still alive, although that's unlikely.
If Mockingbird does make it onto the big screen, it'll likely be as a supporting role, with my best guess being in, once again, Captain America: Civil War. After all, Hawkeye and Mockingbird have strong ties in the comics and I think that it possible whatever side Hawkeye is on during the Civil War (assuming he doesn't stay neutral or die in [The Avengers: Age Of Ultron](movie:293035)), Mockingbird could end up with him. I don't think Mockingbird entering the movies will make waves, but it could pave the path to the rest of the S.H.I.E.L.D. team to come along, which is the same with Coulson.
And finally, Speedball
Kit Simpson Browne, another contributor here at Moviepilot, wrote an article about the likelihood of the Civil War starting in Agents Of S.H.I.E.L.D., mostly through the rumor of an actor who might have been cast as Speedball. Out of everything I've posted here, I think that this may be more likely than any other. After all, fans of the show have been clamoring for an actual superhero to show up and help the team (the closest has been the Asguardian Lady Sif, who was only around for an episode). Marvel could easily show Speedball at the very end of the season finale, then continue to reference him and the New Warriors throughout the third season leading up to Captain America: Civil War.
In short, I doubt that Agents of S.H.I.E.L.D. will play much of a part in Avengers: Age of Ultron unless the weapon in the temple falls into Ultron's hands somehow, which I honestly think is as likely as Iron Man showing up to help the team kick some butt (Hawkeye, however, could be a possibility). The earliest point I can see S.H.I.E.L.D. entering the movies is Ant-Man, and I find it much more plausible that S.H.I.E.L.D. will affect the upcoming [Captain America: Civil War](movie:994409) more than anything.