I just did a quick look at the motherboards at ZZF, ~20 LGA 1366 boards, ~50 LGA 1156 boards, ~50 AM3 boards, that seems like a decent selection to me, its not great but it certainly isnt sparse.
Personally, i dont see small mobile devices ever taking over the role of a PC, people tend to be more comfortable and efficient with a keyboard and a mouse and for higher level tasks like video editing/transcoding and image work, you need a larger screen and a more powerful CPU, so even if the mobile devices have the CPU power, once you have to hook it up to a monitor, keyboard, and CPU why not just have a full desktop?