The "point" is mostly about being able to extend the life of a machine by adding in another graphics card at, hopefully, a dirt cheap price (at that point in the future.)
Your ability to upgrade a processor would be contingent on AMD's sticking with 939... which is likely for a while at least, I guess, abeit uncertain.
As for whether you "should" or not.. thats really a question only you can answer. How big a gamer are you? How often do you upgrade and whats your budget?
I'm jaded enough by issues that I'd rather go with tested technology... thats been out at least a couple of months, when people have had a chance to report widespread issues... so I wouldn't go with SLI just yet myself, anyway.