Last chance to turn away! Spoilers ahead!
Does that mean he's done messing with the universe? Before my second round of watching, I thought there was a possibility that Thanos may not be the villain for Avengers 4. I realized though that the end credits announced "Thanos will return", which I think heralds his "second coming". But if he's already wiped half of the universe, what is there left to do?
Keeping the universe in check. Thanos argues with Gamora that he's the only one who has the sense and the resolve to do what's necessary and keep the universe in check. I'm betting that this is the reason why Thanos is going to stick around. He wants the universe to exist in his way and in his terms, so he's probably gonna be around like a beat cop making sure everything is just the way he wants it to be.
Heroes cut down to half. With the roster of the Avengers back to the OG players with a couple additions like the leftovers of the now non-existing Guardians of the Galaxy, coming after Thanos may seem more of a challenge than it was before.
But I think the playing field has tipped to side of the Avengers a bit. Hear me out: yes, their roster has gotten significantly smaller, but Thanos has also lost the Black Order aka his children. There's also one thing that makes Thanos significantly less powerful than before...
The Infinity Gauntlet has been destroyed. The Infinity Stones may still be intact, but without the Gauntlet, Thanos can't use them. He's going to need another Gauntlet, and this is the window of opportunity the remaining Avengers have to stop him.
Also, Captain Marvel is coming. There's a reason why Nick Fury decided to call her now of all times when he could have called her anytime in the past. He knows Captain Marvel is someone who can turn the tide.
That doesn't mean it will be easy for the heroes, though. They've got a chance to stop Thanos, and obviously, Doctor Strange saying "It was the only way" meant that they were on the path to victory despite it being very, very costly. The Russos have said that Avengers 4 could very well be a three-hour movie which means there's a lot of stuff they want to get into and lots of stuff is going to happen. And though the victims of "perma-death" number but a few (Loki, Heimdall, Gamora, and Vision)...
Avengers 4 could very well mean the demise of those who were left behind. It's cool that the OG Avengers are those that are left, but it's also scary knowing that they're the ones who now have a higher chance of actually dying for real.
And then there's Doctor Strange giving the Time Stone to save Tony. Obviously, Strange foresaw that Tony is more important than the Time Stone. His remark about "It was the only way" meant that somehow, this was the way they were going to win. And of course Tony would be the one to end all this because it all started with him.
But that end may mean Tony's end as well. The Russos have talked about paying the price, something they've shown very, very thoroughly throughout Infinity War. They've acknowledged the fact that we know those who evaporated will be back, but they asked the very frightening question of "What will it cost?" If Tony is so important, he may be the key to bringing back those heroes, but it may cost him his life. He could possibly wield a new Gauntlet for the sole purpose of bringing the evaporated heroes back, but the Gauntlet may be too powerful for a normal human being to wield.
That also doesn't count the others who could die in the battles yet to come. Once again, the Avengers left behind are now on the tightrope. They could die - and die for real.
Can't the Infinity Stones bring them back though? The Russos have been adamant that there are going to be permanent deaths otherwise the stakes aren't real. I'm guessing the Infinity Stones can only bring back the people the Stones themselves wiped out. Anyone else is dead for real.
What's going to happen to the Avengers after all this? Kevin Feige has said before that there's going to be a roster change. I'm betting that the new Avengers are going to be led by none other than Captain Marvel herself. As for the big three - Iron Man, Cap, and Thor - they might retire peacefully or meet their end (knock on wood), but I'm gonna call it and say that they're arcs are done. Doesn't mean they can't appear in future movies. They'll probably have cameos and stuff but they won't be as involved as they are now. Of course, new members of the team will probably include Spidey, Black Panther, and Doctor Strange, and probably some new charries Marvel has yet to introduce. Maybe even some of the Guardians decide to stay.
Bottom line? The remaining Avengers are going to get a lot of help from Captain Marvel. They have a small window of opportunity to find Thanos and get the Stones before he builds another Gauntlet or something that will allow him to fully wield the power of the stones. There's going to be more perma-deaths, and I hate to say it, but there's a big chance it may be Tony and not Steve that ultimately bites the dust for the sake of the team. It's safe to say I think that we'll probably be saying goodbye to the OG Avengers, at the very least the Big Three: Cap, Iron Man, and Thor (in what way we say goodbye is frighteningly up to the Russos). But when the dust has settled, out of the ashes comes a new roster of Avengers.