It hasn't for the last seven years? Other than the arrival of SSDs, the consoles were running on a half-decade old tech and still doing fine. If anything, tech seems to be moving slower lately, with less increase of processor powers and less notable increases in graphics capability.
The last 7 were far different IMO. Coming out of the bubble, and very little progress in software, not much needed to change. But now, I think the fact that software, not hardware, is changing rapidly, a 7-8 year cycle isn't going to work.
Sure, they can bolt-on new firmware updates and operating systems, but I think the way we use consoles will change quite a bit in the next 3-4 years alone.
