In 5yrs/ time you will probably be looking at DX12 or 13 not 10! DX10 will be like DX7 or 8 is now. "Outdated"! And DX10 is already running a DX9 card here along with DX9c. The DX10 simply means that a card "will require" DX10 in order to work properly.
DX10 came out on 2007
DX8 came out on 2001
So, it took 6 years to move from DX8 to DX10
But alot of old cards run DX9 stuff, where as NO old card runs DX10