Most of the apps that sell well originate from a developer solving a need they had, on the system they were using.
If this drives developers from OSX to other OSes, chances are they will develop apps for those OSes first.
Apple is too big to fail at this point, but driving developers away from your platform isn't a very clever strategy. You never know when you are going to hit a tipping point, and after you notice and people stop using macosx for development its already too late.
It took me ~150 hours to migrate to Linux, but my user and developer experience on Linux is much better than on MacOSX (emacs daemon "just works"!!!), so after all that work I wouldn't consider switching to OSX in the next 5 years at least. I had a Macbook air 2012, and because Apple still hasn't released a laptop that isn't a downgrade from that in some sense (keyboard, magsafe, ...) I've went with a think pad instead. Tiny details, like having a webcam that doesn't suck now prevent me from going back to OSX.