Wait and see what happens. Nvidia can now poke around a bit with the GF104 architecture. The GTX460 still has a disabled cluster and might be able to be remedied. Although people use sli as a negative (due to lack of support) there are very few games that dont support crossfire or sli and if they dont, they're probably not biggies as the latest and greatest need the support for optimum marketing.
There's a chance that ATI release a hyped up hybrid in the next few months and i'm pretty sure NV has got something up it's sleeve to counter it (Southern or Northern Islands - can't remember which is the 40nm one and which will be on 28nm later next year- for ATI) and like i said, a full fat GF104.
However, if you must buy now - absolutely sli GTX 460. Overclock well, quiet and power friendly (as such). One GTX 480 is outdone and GTX 480 sli is just as wankish as buying a 4GB 5890.