Depends on future response.
If Zero does very well, then SRK will be encouraged to do more work, otherwise there's no need to work so much when the result is flop and damaging his brand value. He's already earned $750m, how much more does he want to earn?
Salman I think has lost interest and also the kind of movies he's associated with, big mass action movies, he is not able to do those for much longer as he's pretty old now. Still I think at least until he's 60 he will continue.
Aamir will continue to work at a snail's pace for the rest of his career, he will be a lead actor into his 70's. He of course will not be doing bug action stuff but then that's what stuff like Dangal and Forrest Gump remake is for.