Agreed, same goes for feature requests from users (I get a lot more of those than PRs on Aerial).

Yet if it's a decent/good idea, my go to answer is "not yet" and not "no". If it's really a great idea, eventually I'll get to it. By keeping the issue around open, it's still peripherally in my vision and I may have a plan to take care of it that depends on something else. Extra information is never wasted and may inform your decisions on what you are working on now. Plus you know, it's kind of the polite thing to do.

I feel it's the same for the original Steve quote, Apple was/is pretty famous for saying "no" to a good idea and revisiting them later. I think "not yet" is closer to the originally meant intent.