not entirely sure this will affect my choice for CPU, how future-proof would the i7-950 be versus the Phenom II X6-1090T?
That's really difficult to say atm. . as AMD's upcoming bulldozer chip is moving to a format that is on the surface similar to the intel i7 series [calling it a hyperthreaded quad core is a little misleading, but it communicates what AMD is trying to accomplish]
Unfortunately Bulldozer will NOT be compatible with existing AM3 motherboards. They're moving to a new AM3+ socket, which will be backwards compatible with existing AM3 chips.
It seems that the whole hyperthreading concept is what they're moving towards, so I'd have to say the i7950 would be the more future proof one. . depending on what you're doing. I like my 1090t, and after finding out that bulldozer won't be 8/16 I don't think I'll be trying to figure out how to get one into my new rig. . unless the reviews somehow show that they get double the performance of my overclocked X6 ;)
Information source article: http://www.gizmodo.com.au/2010/08/amd-announces-8-core-bulldozer-cpu/