Do you think there will be a point when there will be no more ideas to implement ? even apple in one of it's ads said
"there is an app for just about anything"
"there is an app for just about anything"
I have this really good idea but please don't tell anyone. I want to make a fart application that farts when you press a button. I don't think anyone has made one yet.... oh... wait... lol.
Anyways no, I think there are plenty of apps out there, however there are always new ideas that people haven't thought of, until people find it and go "holy crap I can't believe I haven't thought of this". And then there's the applications that are modified and changed and made better (or worse). Not innovative, but still progresses things.
Depends how innovative you are, if by idea you mean a copy or derivative of what is already out on other platforms then yes its possible to reach the limit. If you have unique ideas then I can't see why there would be a limit. New music appears in the charts every week and music has been being made since humans developed intelligence!