Well I watched this last night and really enjoyed it. It was a really tough to make a film work with so many characters. I had many chuckle moments with the Guardians, really really good.
Plainly the 50% are going to be resurrected that's the goal of the second movie and it does provide an opportunity for the original Avengers to get some serious screen time early on in the next movie.
I'll throw this out there, Thanos is not the bad guy for Avengers 4 in the same way Hydra weren't the bad guys in Age of Ultron. Thanos story has been done really well, the film is about Thanos really his story, his motivations, his victory. He will be defeated in the first act of the Avengers 4 and there is another villain with equally terrible goals but far more evil desires. I reckon Red Skull will be the bad guy somehow taking the gauntlet from a defeated Thanos. After all the story is very Earth centred, Thanos almost doesn't work because he's an external threat. For resonance the threat has to be human, our failings we're fighting. Roll out the Nazi a threat for Earths greatest heroes to beat a suitable end for the WW2 hero to sacrifice himself. Just my wild ass guess. I just have difficulty seeing how you get another 2 or 3 hours out of Thanos now he's won.
edit: Oh yeah and was I the only one that thought Stark's Iron man armour is getting a little ridiculous, shape changing nano nonsense.