Originally Posted by HTupolev

SRAM pulled off the 12-speed MTB cassette partly by making the big cog so huge that it could sit out over the spokes, rather than just on the freehub body. On a "road"-sized cassette, you'll have to squish the extra cog on the freehub somehow. There's not much room to increase wheel dish at this point, so probably either the bicycle frames will need to get wider or the chain/cogs/whatever will need to be made considerably more narrow.