For tech news fans (yes I'm a tech news fan)...take this however you want it...
DX10 is only for Vista...that may or may not change depending on if they can overhaul certain parts of XP, etc
DX10 hardware may come out before Vista. Purchasing current gen, non DX10 hardware does not prevent you from running/using Vista.
You can buy current top of the line DX9 hardware, upgrade your OS later to Vista, and have to do without DX10 support.
DX10 products may not REQUIRE DX10, but only performs better with them.
To this individual, me...I have hope that ALL of us, who are not waiting for DX10, can at a later time, purchase DX10 auxilliary cards. Such things are possible...but may or may not be profitable to the industry makers, ie., ATI, Nvidia...and even Ageia.
It is the same principle behind those cheesy electronics sales people who try to convince unknowing consumers that they HAVE to buy digital HDTVs because their current SD tvs would cease to work...when all that would be involved are scan converters.
Of course, if the entire industry says NO to the consumers...well then we'll just have to take one for the team. eww
Just keep in mind, what I said about DX10, though true, could and might change...but just think that it won't and you won't be so depressed ;p