Heres my 2 cents, since nvidia already has the strongest video card on the market in terms of gaming performance ( no arguments please, look at benchmarks in games ), if the 9800 gtx comes unchallenged in terms of performance you can SURE bet it won't be 650 when it comes out. More like 850 at least I'm guessing...
like heck retailers are going to sell it for MSRP when its brand new and the best you can buy...If you can wait, you will probably need to wait till early 2008 at least to get a decent deal on a 9800 gtx. The 8800 gtx however price will probably be cut in half in november, you decide whats the "better deal"
and to all those saying they want to SLI the 8800 gtx...I strongly advise against it unless you got the best cooling and lots of space. Heck 1 8800 gtx runs hot enough STOCK! I can't even fathom how much power two would take and the heat they would generate running overclocked! Even thought I have a 8800 gtx ill prob just wait 3-4 years till it gets old and sickly and get a 9 series card instead of going the SLI route, no matter how cheap 8800s are.