"Will we be able to develop 64 bit, DX10 games?".

In time, yes. But not soon.
There is a lot of interest from the programming side but there are not many users set up to run such a game. Right now, you would be lucky to sell 2 copies.


My understanding is the DirectX9L doesn't run on top of DX10, but it works just like DX9 does on XP. The difference is that DX9L is for Vista, and Vista has some new features that should make DX9 games run faster and safer.