I don't know that I'd count on future compatibility. Even if gaming can take advantage of all 6 cores, games aren't generally CPU intensive, and the ones that are generally aren't GPU intensive (RTS) and still won't really hog all an X4 has to offer.
Let's look at a review shall we?http://www.tomshardware.com/reviews/amd-phenom-ii-x6-1090t-890fx,2613-9.html
Same thing, overclocked:
X6 just isn't a gaming CPU. It's for professional applications for encoding and similar CPU intensive utilities.
That said, for only a $20 difference, and looking at the relatively small FPS difference, the X6 is a good deal. Also, make sure you get a DX11 GPU since DX11 supports multithreading much better than ever before (DX10.1 and lower)