In The Avengers, we learned that Iron Man was more than willing to sacrifice himself when lives were on the line. In fact, he once again came close to meeting his maker in Avengers: Age Of Ultron while struggling to save the world, and so it's hard to escape the feeling that Tony Stark is destined to go out in a big way. With no Iron Man 4 in Phase 3 (despite the fact that the last instalment grossed over $1 billion worldwide), Marvel clearly aren't in a rush to get back to the character's solo franchise, so killing him off in the second half of Avengers: Infinity War to bring this era of Marvel movies to a close could definitely work. However, having him going down swinging in a fight against someone like Thanos doesn't quite feel right; Iron Man's sacrifice would have to be bigger. By now, Tony has proven that he's the kind of man who will give up his own life to save others, so Iron Man being forced to stay behind in outer space (with his oxygen levels running low) for some reason while his fellow Avengers return to Earth would be a very meaningful moment, but also ambiguous enough to lead to a possible return. Alternatively, it would be pretty great to see him go out with a bang, blowing up his Iron Man armour - with him inside - to wipe out Thanos' forces for good.
