Can a dx 10 card be patched to a dx 11?

I suppose you could software emulate the features, like NVidia may be doing, but it would be a ton of work for horrible performance, so I doubt it. I think some Intel IGP's did software DX10 (though did it horribly, I should add). Also, why would they want to give you a reason not to upgrade. So no, it won't happen.