We managed to confirm the existence of DirectX 9.0L but it won't be a DirectX 10 for Windows XP. It will be the other way around. It is a faster version of DirectX 9.0 that will run under Vista only.
So I have to disappoint all of you who expected to run DirectX 10 games under Windows XP (and apologise, huh, Fudo? News Ed.) as there won't be an API to supports it.
DX9.0L is a special version of DirectX 9 for Vista only that allows DX9 games to run with Vista's new driver model. It's not possible to run D3D10 on XP without running in pure software emulation.