From what I've seen, there hasn't been much of a mass-market need for large improvements the past couple of years.
I've been PC gaming since '96. The cycle has always been nearly the same. At around the 3 year mark, the PC would start to feel sluggish and I'd start to get the bug to build or buy another one. Before four years, it would become intolerable and I'd pull the trigger.
I'm now sitting on a PC that is just shy of 4 years old, and there's very little I can throw at it that it doesn't handle easily. For general computing, absolutely nothing taxes it. On the gaming front, Bioshock Infinite was the first time it ever started to feel a touch behind the times. I don't try to push the latest Crysis at Ultra settings. All this while running a Plex server and other background stuff.
For a while I'd been thinking that Haswell would be a good upgrade for me. And it's not to say I wouldn't see some rather nice improvements, but when I started looking at it seriously, I realized it wasn't a good value. I wasn't comfortable spending the money I would have to see the gains that I expected, especially considering what I have is holding up quite well. Quite frankly, the gains per generation were not particularly impressive from my perspective.
With the increased focus on mobile computing and power consumption, I've felt for some time that the traditional PC is seen by the industry as "good enough" (and lets face it, for a vast swath of normal users it really is). There's not a lot of gain to be had by focusing research effort on the enthusiast folks. Way back in the day "pushing the envelope" was buying the $150 graphics card instead of $100. When I spent $270 for a card in my last build, I shook my head a little never expecting I'd pay that much for a card. Now the highest end is double to triple of that. Don't get me wrong, I"m not saying you don't get something for that money, but it is costing more and more to see such significant jumps in performance.
I think we're at an interesting turning point today. Traditional PCs are going to be less and less relevant, and I (sadly) can picture a world in 10-15 years where an enthusiast gaming market simply cannot sustain itself. On the other hand, it's my strong hope that with the new consoles launching soon, there will be new life pumped into the market and there will once again be a need and desire to make significant gains in performance.
(Before someone misquotes me, gaming won't go away, but it could easily take on a different form from PC/x86. What we do today simply might not be relevant or possible.)
This has me looking ahead though, wondering when cell phones will reach that same "good enough" point and start to stagnate. It's both scary and wonderful to be able to watch the life cycle of these things in such a relatively short period of time.