Sram XX1 is trickling out to a few lucky riders and we are regularly asked what hubs are compatible, or indeed which are upgradeable at a later date if you decide to splash out, or wait until Sram 11-speed trickles down to cheaper groupsets.
The good news is that as far as we know, pretty much every rear cassette hub will be upgradeable with a freehub body change and a drive-side spacer - so no need for new wheels, unless you want to of course. As of mid-December 2012 when I wrote this, XD-driver (the official name for the freehubs) conversion kits are available now or in the near future for these hubs:
American Classic Disk 225 (available now)
Hope Pro 2 Evo (available now)
DT Swiss 240 and 350 (available now)
Industry Nine (available now)
Stan's NoTubes ZTR 3.30 hubs (end of March 2013)
At the time of writing, the latest unofficial word from Chris King is that they may make one in future but are too busy at the moment.
We don't yet have them all listed on the website so if you need a wheel with an XD driver, or a conversion kit, please contact us and we'll get you one.