Well I built my latest gaming rig the week before Skyrim was announced and I won't be able to afford to upgrade if for a while.
So no forewarning or planning for me! However I am confident that it will run well on my current rig, this isn't like days gone by when a PC would be obsolete within a few months of building it, most games are built to run on consoles and thankfully that has kept the PC hardware requirements in check somewhat.
I have an AMD Phenom II 3.40GHz quad core, ATI 5850 GPU, and 8Gb RAM.
Noting from recent similar threads on this forum, a lot of people will jump in and tell you that 8Gb RAM is overkill - and yes for a lot of things it is, but it depends what else your PC will be doing. Play CIV 4 with the type of mods I use (ROM, AND, AND Mega Civ Pack), and 4Gb doesn't quite cut it! But I have 8Gb mostly for that modded game, Skyrim on Win7 will likely be fine with 4Gb. Although if you're thinking about building a PC in the near future it's probably worthwhile waiting a couple of months to see what the official minimum/recommended spec is, and also to scout around for bargains on component prices