I have GT SLI and I am thoroughly impressed with it. I say go for it. If you want your games to look better now, then buy for now. I've never been one of those that will "wait on the next thing" because you can garuantee that A. the next thing will be expensive as hell and B. once the next thing comes out, the value of your current stuff will decrease even more.
This is great advice. Also, if you buy eVGA, you can upgrade in their buy-up program. I'm not sure if it will include the next generation of cards, but you can buy now, and have 90 days to determine if you want to buy up through them. Something to consider...
HomeyFoos