Think we just hit the point where games just don't need nothing better then a 2500k.
we hit it before the 2500K was released. It is consoles / console ports (as other have mentioned).
Any improvement will be questionable as I see it as it will need a new console range to up the performance limit. But given that Microsoft and sony like saying the consoles are a "10 year" item (or something to that effect), then we still have a while to go. Not even romours of a new console from those two.
Of course, inital release will be like the xbox->xbox 360 change over. Most games for the newer unit was more of a graphics update to the same program code. Actually taking advantage of it was another 12 months.
Given that, it will be something after Ivy bridge's successor that will be in line as the current system when games take a "step up".
And by "step up", it is not going to be a great thing for most people as TV's that the consoles use will still be 1080p units. So same screen size will proberly more detail and greater distance generation. Like that helps with some game types. AI might improve with more cpu time to work with, but I suspect game developers will skip that feature as AI is not needed for playing against other humans. So even a better single player experence is also shot as being viable in the future.
The more I think about the future based on what I see/read/hear is that the gaming style I grew up with is gone. The replacement is the console/mobile phone that I do not find attractive. By the time it comes back around (if it does), I will be too old / out of it too long to care.
Only reason for a increase in PC performance I can see is for non-gaming tasks, and I do not do that many that often.
It is nearly sad enough for the tinker in me to think that my next "gaming machine" will be a laptop (possibly a desktop replacement class, but still a laptop).