Pretty sure that, sadly, Marvel has confirmed they're not doing an Adam Warlock story. Rumor is he won't even make it into GOTG 3.

Didn't James Gunn say that he would be part of GOTG3 like a year ago?

Yeah, but there's been buzz that it might not happen. Here's hoping, though.

Also Thanos looks boring without his hat. Thanos with no hat is just purple dyed wrestler with chin scars.

Meh.

He looks like the Thing, if the Thing was even more Thinglike.

Maybe market research figured out purple and gold was too gay for certain territories.

Well, maybe for Dean and Frank. But I don't remember Sammy getting a fanboy moment.

No, this is Giant Purple Guy.

Totally different than Giant Blue Guy, Giant Silver Guy, Giant Rock Guy or Giant Giant Guy.

I BET THERE'S A PORTAL THAT NEEDS TO BE CLOSED.

If they follow the comic story to any degree, it won't be about portals or anything like that, but: Thanos becomes powerful enough to reshape all of reality, but in his hubris and ego, allows room for the possibility of someone defeating him. Given the amount of time they spent in GOTG2 making sure you knew that Nebula and Gammora were Thanos' "children" and fought for his favor only to wind up hating him, I would assume at least some elements of the comic are going to be used and his undoing will be his ego and the assumption that Nebula is still loyal to him or not a threat.

It's not Venom but one of the Outriders (nice insert there, Marvel), a race of monsters basically made by Thanos to serve as assassins.

That said, given the visual similarities, how much you wanna bet that this will be the way they write in the Venom symbiote.

I'm guessing they'll knock off Captain America as the big 3rd act twist and to motivate the heroes for the 2nd movie. He's been very vocal about wanting out to start directing. They'll repaint Falcon's suit to match the comics and he'll be the new Captain America. This way they'll please the fanboys and tick demographic boxes.

Also, Hulk will come out of the closet and Vision will resurrect but now look female.

Just saying, this is Disney now so demographics count for more than anything.

If anyone dies permanently, I'm guessing it will be Iron Man mostly because RDJ has been talking about wanting to leave the franchise, he's only contracted for one or two or MCU appearances, and apparently his salary demands are starting to balloon out of control.
Also, there have been strong industry rumors they want to recast Iron Man into the current incarnation from the comics where it's a black teenage (I think?) girl. We'll see I guess.

Chris Evans will probably leave the MCU (again, his contract is up soon and he's been talking about wanting to leave) but not die. The Captain title will pass to Winter Soldier or Falcon.