BF3: Wait for HD7xxx or upgrade now?

I currently have a GTS 450 w/ an i7 2600k(lol). Running 1080p on my main monitor and 1600x900 on my 2nd which I only use for school and work.

Should I go ahead an upgrade now or wait for Southern Islands? Even though there's no word on the release date.

I'm looking to play BF3 and I noticed they suggested at least a gtx460... is southern island going to be that much better than what's currently out?

Also, whichever route I choose I plan on getting a second card for even better performance(a year from now or whenever I think I need it). With that in mind, should I look for a card in the 175-225 range then match it later when I go crossfire or would it be better to get something good like 250-300 ish and run single?