M.2 PCIe Possibilities?

Aside from adding an SSD or two, I wonder which other devices people will add to these systems. Could new wifi modules be installed in those ports as the standards evolve? Or is there some limit to this based on the configuration of the board, power draw, etc? Maybe an M.2 GPS card could be used to add a high tier time server to the network? Aren't there some system-on-a-chip designs for this port, or FPGA boards at least?

At any rate, this looks very maintainable compared to the molded plastic contraptions in a similar price bracket at big box stores.

IMO it'd be nice if future models begin to settle into the same form factor: the old Linksys models which were designed to stack on each other were a very optimistic choice vs how the market has evolved so far.