I like that idea. Primarily because it means many Avengers movies. But its a minimalist ideal when you think about it. They should really be striving to keep our main cast as long as possible (short of keeping them around with grey hair). The core four should hold out for at least a trilogy of Avengers and MCU phases. Plus an Avengers without Iron Man/Hulk/Thor, while possible, seems to me... somewhat dull. Personal opinion of course.