What I'd like to see is better support for compression at the hardware level, or flexibility that allows it.
Everything you need to support compression is a good out-of-order CPU.
I could see microsoft retrofitting the HD Photo (JPEG XR) format for texture use. Given it already supports mipmaps, HDR and as many channels as you want.
But it's not very local, unlike DXTn; you need to touch tens, maybe hundreds of bytes to decompress a single pixel; and with geometry densities climbing ever higher, it's getting harder to count on good hit rates in the texture caches.