Honestly? Trade up, I mean i love the quad sli, and they do outperform the 280 GTXs in sli in alot of the benchmarks...but the 280 GTX has alot to grow, its still in it mature drivers, and SLI will be more beneficial.
Plus the 1 gig RAM would be a bonus for bigger monitor in the future (plus games that require higher Textures:))
Even I just ordered tri 280 GTX OCXs through my friend's company.
Although I'm not going to use them till 2 weeks from now, I'm very happy with the quad performance for now:) (In other words I'm lazy to swap em hahaha)
My opinion, where performance stands to date (it can change depending on drivers)
280 GTX trisli > 4870 x2 CF > 4850 X2 CF > 9800 GX2 sli > 280 GTX sli > etc..