Interesting question. It's worth noting, though, that it's not at all uncommon for games trying to reach a large consumer base opt to use DX9 instead of 10 and 11 (or, they include it as a fall-back). But for something like Original Sin, a DX11 implementation could actually help to make the game run more efficiently on current hardware, given some of the lighting effects and so on included in the game, so I can't imagine they wouldn't add a DX11 mode at some point.