Well, the suggestion to use the Igromir spec as a minimum sounds good, but other than that, why not wait and see? This forum will be full of posts day one of persons sharing their experiences, be sure
Do like Oleg said and wait until the release before buying a new rig... Being a developer myself I guess much of the work now is optimisation so they probably don't know it themselves now. Every day they hope to find the magic trick that increases the fps 30 percent with the same quality. That's what you do the last months when all features work without major bugs... Squash bugs and find smart solutions to improve the performance.
I sit on a rather old rig (Core 2 duo 3.3, GTX275, 6gb ram) and guess it will work... If not I am pretty sure a new graphics card will be enough to give me the fps needed to enjoy it...