If direct x10 is comming soon to a microsoft site near you. I would wait before I upgrade my video card. But that is just it, I have no clue? Rumor has it Direct x10 will be coming out with Windows Longhorn!
It's now called Windows Vista and Microsoft hasn't said anything about DirectX 10, it most likly will be released with it, as well as Xp SP3 but that's just a guess.