I've got a 4890 that does 60FPS, which is the minimum for me. I'll update when games come out that it can't cope with, but not before.
With the consoles dragging back game innovation, that may be a while. All the PC games seem to be nowadays is hi-res versions of console games. This is okay, but I've just bought a 24" 1920x1200 monitor, so I'm not going to buy a 30" just to make buying a top card worthwhile.
WHat we normally get after a console release is 18-24 months of console led developement followed by 36-48months of mostly focusing newest and best things on PC with a fairly large disparity in quality in looks/physics/power etc etc.
The trouble is this generation, that DX10 was so neutered we didn't really get the normal speed, quality/iq increases in the last few years that would normally have stretched the PC side of things far futher ahead of consoles than would normally happen.
Its like anything, the best coders want to work on the best/newest things because its at the forefront of technology, the best coders/dev's want to make the best games using the newest methods. Unfortunately I think, the improvements we should have seen, more particles, better optimisation to be able to add more particles, higher IQ using tessalation and a bunch of other things, never really happened. So while you can make the same game run at a higher res and speed on a PC, theres not really much you can do on a PC game you can't do in a console game right now.
With DX11, hopefully we'll have that gap finally widened, aswell as simply the massive increase in raw horsepower, higher programability, higher IQ and better ability to push games forward, that dev's will finally be excited to develope for the PC over consoles and can probably do things consoles simply aren't capable of.
AS for missing a gen, I'd never miss a generation, its simply not worth it, ever.
I can sell my 4870x2, I dunno, for £150, maybe even £200, not sure how much they are selling for second hand, and pick up a new card for £200-300. If I wait for a 6870 in 12-18 months, well, my 4870x2 will be worth £50, it will basically end up costing me exactly the same to upgrade once ever 2-3 years, as upgrading yearly because of lost value on old cards. So for the same cost, you can have the fastest card around with every generation.