I'm not usually an advocate of the waiting game but dual 7800gtx's are fast enough for any games that are worth playing (i.e. not STALKER, the reason I bought my 8800gts
). I would hold off until we at least know what the g92/g90/whatever else The Inquirer has called it before you pull the trigger.
Having said that, the 8800s are great cards and if you feel the need to upgrade right now I would get an 8800gtx from eVGA. At least then you can step up if the 9 series does arrive on time.
edit: And I agree with the above posts, upgrade your CPU before your GPUs. A cheap and easily OC'd Core2 will dominate any old Pentium 4.