I do a lot of development on the Mac, and while I share this concern, I haven't been blocked in any way that I would say I'm feeling squeezed out, CLI's still work, all the code I compile still works...

I haven't run into an issue with the "App Store and identified developers" yet, tough I assume I will at some point. But I actually don't mind that as a means of helping prevent some malicious software from running on my machine.

That's not to say I'm not worried Apple will lock it down more, but I think that would really kill the platform, right now it feels like an ok balance.