Canon EOS M is that there will be an EF lens adapter released at the same time, which allows you to use the Canon EF lenses on the EOS M.
But if you are a micro 4/3 or NEX camera owner who also own some Canon EF lenses, you are in luck! Kipon has just announced that they will be releasing a Canon EF to mu4/3 or NEX adapter with electronic contacts that allows you to control aperture
and presumably, autofocus., but most likely, not autofocus.
There is no word on price or availability, but stay tuned for more info!