Then Bucky and Sam would fight on who will be the next Captain America in The Falcon and the Winter Soldier. Then Iron Man will get his own 4th movie like Thor. Or Iron Man might be in Doctor Strange 2.
Tony was done after Endgame, dude was pushing 50. He ain't showing up until Doomsday. He really didn't even wanted to fight in Endgame but was dragged into it cause it was a way to bring back his Dead adopted son.
Mostly, people believed that Stark was someone who would never sacrifice himself for someone else (as Cap said). Apparently the filmmakers wanted to show fans that Tony finally understood his mistakes (and that the heroes will also respect Iron Man) by making the ultimate sacrifice.
