The next gen AMDs (AM2) are due out this year. They will move to socket 940, a 533MHz FSB and DDR2 RAM. What this means is that the upgrade path for the current socket 939 is very limited.
I think you read something wrong. AM2 will continue to use the on-die memory controller after the fashion of current AMD64 CPUs, and such such won't have a FSB. And considering that the HyperTransport bus of current AMD64 CPUs is already 1000mhz (effectively 2000mhz)....
What you see in the S939 market now is all there's going to be, btw. Unless AMD is sneaking something in at the last minute, FX-60 is the last S939 CPU.
Vista IMO will have little impact - while the top tier version of it will be a "gaming" version, there's nothing so far to convince me that it's worth upgrading to in the short term. Not to mention that it will be the latter half of the year until it's out - at best.
AM2 vs S939 is debateable. The initial AM2 system will be roughly on par with current S939 systems, so unless you can wait 3-4 months (or longer) to upgrade and are willing to pay the premium for the newest stuff, S939 is still the way to go.
The only other thing worth considering is that the first gen DX10 graphics cards should be out around the end of the year also.... but if you're needing an upgrade now, that's a long time to wait...
AMD's new processor will not move to socket 940 but rather socket M2.
AM2 is a 940 pin processor, just with a different pin-out so that it can't be mistaken with current (Opteron) S940 models.
However, when the M2 CPU does come out, I will upgrade my 2 home PC's to Athlon FX-60, as its price shall drop considerably.
I wouldn't count on it, at least anytime soon. The initial 6-8 or so AM2 models will be identical in clock speed and L2 cache to models currently on the market. IMO S939 will be very competitive with AM2 until at least the last few months of '06 when new AM2 models start coming out.