are there any BIG reasons to hold off on buying a new gaming rig?

i'm in the market for a new gaming computer, andc cost isn't much of a concern to me

my main concern is that i will buy a new computer, and then some brand new piece of hardware will come out that will be incompatible with my motherboard

for instance, just after i bought my last computer, PCI-E slots & cards came into existence, so i was unable to take advantage of that

so is there anything like that coming up soon that i should wait for? or am i safe buying a new computer right now?

i want something that will last me a few years, and i was thinking of getting something along the lines of this:

 Intel Core 2 Duo E6700 CPU
ASUS P5N-E SLI Motherboard
2048 MB DDR2-800 Memory (or maybe 4GB)

640 MB GeForce 8800 GTS PCI-E Video Card

will the current DX10 cards be up to snuff for games like Crysis, or will i have to buy ANOTHER new card when that comes out?

yeah, i'm not 100% set on any particular graphics card.  i just want something in that same range of quality.

 and price cuts aren't a big concern.  i figure if i wait for price cuts, there will be newer better by that time anyway, and i'll end up getting that instead.

 i have XP on my current machine and i'm happy with it.  i just know that i'll be going to Vista eventually, so i'd rather just get it right away when i get a new machine, instead of making a change after a few months.  i assume Vista is pretty good with the live updates, like XP seemed to be.  a full service pack would be nice, but it could be a while before that happens, so i think i would be happy with live updates as they come.

the introduction of PCI Express 2.0 later this year.Crunchy_Pickles