I think you should be more than covered for whatever comes out. You can always go to a c3 stepping Phenom II, Phenom II X6, or a bulldozer. Any game a 955BE can't handle, I expect will support 6+ cores. The GTX 460 might not cut it if you really wanna smash face with maxed settings and filters on the newest games though.
Regardless, here is how you evaluate: Take whatever game you like, and go look at benchmarks. The 1024x768 benchmark on like jank settings is there to tell you what framerate the CPU is capping the game at, so long as the bench is done with a good GPU. By 1280x1024, you may see some GPU limitation come into play. (You will generally find a good set of this information in CPU benchmarks of a game.)
Then you wanna go look at a benchmark done with some blazing fast i7 at like 8million gagillion terahertz of omgicanrun80versionsofwinraratthesametime cpu running various gpu's at 1680x1050 high settings, this is pretty much gonna be GPU limited unless it's an ancient game in which case it won't matter or some game that uses more CPU than GPU at that res, which AFIAK doesn't exist except in the trivial case of well hmm, am I getting my 280 fps cap from the cpu or the gpu... *looks concerned*
Anyway, whichever number is lower, your gpu with psycho i7 or your 955 cpu at 1024, that will pretty much indicate where you are being limited. I'm sure there are cases where this is wrong, but I think it's generally a pretty good indicator. BETTER IDEA: You can run your own CPU "benchmark" by monitoring your avg and min framerate at 1024 if you can't find someone else doing it, then compare that to your framerate at 1680 w/ good settings, if they are the same you're CPU limited, if the 1680 is slower, you have at least some GPU limitation.
AFAIK there aren't really any games out that are gonna be held back by a Phenom II X4, as it will provide like 80FPS in most games if your graphics card can keep up.
My guess is you're going to want to replace the GTX 460 long before you become CPU limited. You could go with an SLI setup (which, depending on what you have, will require another GTX 460, an SLI motherboard, and a spiffy power supply.) However, from what I've seen the 460 isn't even much better than a HD 4890/GTX 275 at your resolution and costs a lot more, so I wouldn't even bother.
I'd move up to a 6950 1gb/6970 if you see the need. If they ever release a 6970 1gb that would be perfect. In fact you might want to dump the 460 while it still has the mystique of being remotely new masking its mediocre performance.
BTW, Intel CPU's are bloody amazing and absolutely the performance kings and benchmark masters, and they are a good value in terms of benchmark performance per value, but in terms of gaming performance for value, they are pretty far behind AMD right now since a graphics card will cut off the unrealizable frame-rates intel cpu's can provide at the same place it will for an AMD.
.