That's not quite as silly as it sounds, a pro photographer I know has actually been using a Nikon 1 with his 200-400 for photographing golden eagles when he needs extra reach and the quality was actually better than I would have expected.
I heard they're going to kit this with the next Rebel.
I heard there will be an EOS-M + EF-EOS M adapter bundle with the 800/5.6 II.
That's only because the pixel density of the Nikon 1 is greater than any other interchangable lens camera Nikon makes. Putting a super tele on an EOS M is pointless because the pixel density is the same as the 7D (which is considerably better than the EOS M in almost every single way), 60D, T2i, T3i and T4i.