There has been NO confirmation about any of this. Just fan speculation. These are my thoughts on how it should go down. If you don't like my idea, it's fine, just tell me, you are entitled to your opinion.
I'll do transitions because say some people feel like Iron Man should fight Star-Lord, well others would say Captain America should so things will happen in the battlefield to allow both battles to happen.
NOW LET'S GET STARTED!!!(:
This would happen no earlier than 2018. If the Avengers and the Guardians meet up, they need to fight first and then team up. That's just how I roll with heroes. I have it go the same when I do Avengers and Justice League stories. One question is WHO will be on the team when they meet? It won't be just the core six Avengers or the original five Guardians (Is Yondu a Guardian in the MCU? I am not really sure.)
Lets get a headcount here (hehe see what I did there(;?)
Current roster: Captain America, Iron Man, Thor, Hulk, Black Widow and Hawkeye.
Possible/confirmed additions: Falcon, Scarlet Witch, Quicksilver, Vision, War Machine, Mockingbird, Black Panther, Ms. Marvel, and possibly Ant-Man (Scott Lang), Wasp (Hope van Dyne) and Spider-Woman. I know that's A LOT.
Most likely roster in 2018: Captain America, Iron Man, Thor, Hulk, Black Widow, Hawkeye, Black Panther, Ms. Marvel and Falcon. This is just for the Guardian meet. I'm sure they'll go all out in Avengers 3 for the roster.
Guardians of the Galaxy
Current roster: Star-Lord, Rocket, Gamora, Groot and Drax.
Possible/confirmed additions: Adam Warlock and possibly Yondu, Quasar (Pyla-Vell), Nova (in case you haven't heard, James Gunn only wants one Earth character and that's Star-Lord. So Richard Rider won't be Nova. I suggested that they make Nova a Xandarian or completely different species or gender.), Major Victory (origin change) Mantis (origin change), and Moondragon (origin change).
Most likely roster for 2018: Star-Lord, Rocket, Gamora, Groot, Drax, Yondu, Adam Warlock, Quasar and Nova.
HOW WOULD THEY MEET?
Say after Avengers 2, they have space capability and want to find a place to store the Infinity Stone that powers Ultron. I am one of the believers in that stone being the Soul Stone. So the Avengers are flying through space looking for a place to store it. Their ship is engaged and is forced into evasive action. I don't know if the Blue region of the Moon is in the MCU, but for lack of a better place, that's where I'll have the fight--a compound on the Blue area of the Moon. After a cool space chase scene, the Guardians knock out an engine to the Avengers' ship and they are forced down. As this happens, Iron Man and Ms. Marvel fly out. Iron Man is slowing the ship's descent and Ms. Marvel shoots the Guardians down. Both ships are grounded. Each team runs out and they are facing each other now, no too far away. Close enough for them to hear each each other. The reason they fight is similar to why Iron Man and Thor fought in the first movie. You always need that comedy element in a Marvel movie so here's the dialogue below.
"Cap this a tree, a raccoon, two green people and dude who thinks he's cool cause he has rockets on his boots!" -- Iron Man
"Stay focused and pick your targets" -- Captain America
"Are these mortals mad?" -- Thor
"Aye, but Wakanda has seen it's fair share of foolishness" -- Black Panther
"Uuuummmm....." -- Hawkeye
"What he said" -- Falcon
"I missed a S.H.I.E.L.D. op for this?" -- Black Widow
"Can we mop the floor with these guys already?" -- Ms. Marvel
"HULK SMASH!" -- Hulk
"I stand corrected, there are bigger idiots in the Galaxy than you guys" -- Gamora
"What did he say about my rocket boots!?" -- Star-Lord
"What a bunch of queers!" -- Rocket
"I am Groot" -- Groot
"This course of action is illogical, we will totally destroy these tourists" -- Drax
"My arrow take all these ones out then we be on our way for a drink, Quill!" -- Yondu
"They have the Soul Stone!" -- Adam Warlock
"Blondie's mine!" -- Quasar
"These are the Earthlings you talk about, Quill?" -- Nova
I would have the Marvel Comics and Marvel Studios logos on the screen and have this dialogue going and have the screen black until it is done for the trailer. Then show them face off, charge, then BOOM! Avengers: Infinity Gaunlet. Coming to you in summer 2018. Then have awesome music playing and show little bits of each fight and the dogfight. That would be the trailer!
Iron Man vs Nova
Captain America vs Gamora
Thor vs Drax
Hulk vs Groot
Black Widow vs Rocket
Hawkeye vs Yondu
Falcon vs Star-Lord
Ms. Marvel vs Quasar
Black Panther vs Adam Warlock
Remember what I said about transitions? I used these same transitions for Avengers vs Justice League. Here's what I mean:
Most of you have probably played this game. I also think environmental transitions should happen too. Meaning a building might fall and say Panther and Warlock were fighting. They both jump off, but go to a different area and fight a different opponent, etc.
Skip to 8:35 to see the Avengers and Guardians fight and team up
THE TEAM UP!
The Avengers and the Guardians have their fun fighting it out and then stop eventually. They each tell each other what's been going on and their encounters with Infinity Stones. Then afterwords, they find the Soul Stone is missing. "WHERE IS THE SOUL STONE!!!??" While they were fighting, someone came to the Moon and stole it.
"Jarvis, play on board recording through my helmet and project." -- Iron Man
"Quill, who is that?" -- Hawkeye
"Her name is Nebula, archer. A daughter of the mad titan Thanos" -- Gamora
"Why does she want it?" --- Captain America
"Why did you humans want the Tesseract?" -- Drax
"Point taken. What do we do now?" -- Black Widow
"Thanos means to complete the Infinity Gauntlet ya morons! Ain't it obvious?" -- Rocket
"We have to take out Thanos. Only our combined forces will maybe take him out" -- Star-Lord
So with that being said, they find Thanos and engage him. They are getting whooped of course in the beginning.
But then again, the MCU won't work with heroes just dog piling a villain. Thanos will bring friends.
Skip to 10:00 so you have an idea about Thanos.
Here's how I imagine the final moments of the battle!
Cap would be a lot more battle damaged when he says this though and without his mask. Here's how I would have it go:
"I'm not the one who is about to die"
As he says this, Thor and Hulk hit him wit a combo. Skip to 40 seconds.
Only the combo is from a different angle. Thor comes from the right and hammer gets a solid hit on the chin. Hulk comes from the left and gets him. As Thanos is airborne from this
"I AM GROOT!!!!" -- Groot
Groot knocks him back, but Thanos grabs him and brings him with. While it looks like Thanos will rip Groot apart, Thor and Hulk throw Drax at Thanos.
"THANOS!!!!!" -- Drax
The extra push helped a lot.
"YOU KILLED MY WIFE AND MY DAUGHTER!!! YOU DIE" -- Drax
"You insects amuse me" -- Thanos
"Not exactly the word I'd use" -- Captain America
Captain America, Iron Man, Black Panther and Gamora do strike and retreat tactics on Thanos and return to fighting the other enemies. Star-Lord, Quasar and Ms. Marvel are striking from the air.
"ENOUGH!!" -- Thanos
"I couldn't agree more--ENOUGH!!!!" -- Drax
As he says this he does....THIS!!(:
I know this would be altered to where some heroes will die, but other than that I think after three and a half hours, I should post this! Whaddya say!?(:
I had one idea about them meeting through the Inhumans. It was a while ago, but someone posted that they could meet through Doctor Strange.