It's an interesting point people are making about the processors reaching a level where performance plateaus. I've been on the iPhone upgrade programme for a while so I don't know if recentish iPhone suffer slowdown like old ones did, and my current iPad is of course more than fast enough. If CPUs aren't a concern anymore, RAM I suppose could be, but I'd be surprised if that becomes a concern for the OS in the next few years (but will be a concern for being able to run the latest apps).