DX10 G80 is November, utterly pointless for DX10 as DX10 can't be used till Vista comes out (Feb time), and the first game that will use it (Crysis) is supposed to be March, so why anyone wants to buy a DX10 card in November is beyond me, March is 4+ months away from then, by which time the refreshed, faster, better G80 will be out, also R600 (supposedly Vista time) which will also be pointless, id buy a high end card now and use it for a year+, as it will last that long, and DX10 may be used more then, and worth having, pointless for Crysis and the other DX10 games, as they all work in DX9 also, and under XP, so theres no need for your £200+ Vista either, on top of your £400+ DX10 card.
Looking at Crysis in DX10, it looks identical to DX9, so why spend £200+ on an OS, plus £400+ on a DX10 card so you can have it running identically in DX10 to DX9, but just a bit faster, and if you have a high end DX9 card, its going to cut through it anyway, or you could just keep your low end card until G80 comes out as it will be the fastest DX9 card around, but an absolute pointless upgrade for those with high end cards, DX10's not worth having for over a year yet, G80 is only worth it for DX9, as thats all it can be used for for months, so as i said if you have a high end DX9 card already cutting through DX9, then G80 is gona be pointless.
I wouldnt hold off, a high end card will last well over a year, you think G80 is gona still be top dog in over a year, not a chance, theres gona be loads of new cards by then, so you can get one of those for DX10, thats if its being used more and doesn't look like DX9.