Yawn. If Canon would look to the RX1 for some inspiration, then I might consider it.
The RX1 is priced like a 5D III and has a fixed lens. The EOS M is - and will be - an interchangeable lens camera for the masses. The RX1 is nothing more than a marketing exercise. Takes good pictures, true, but for the price of a 6D or a D600 and a Sigma 35 1.4 you'll get equally good pictures for less money. And you'll be able to put other lenses on it.
As well, full-frame sensor is absolutely unnecessary. Besides the fact that you can take gorgeous pictures with a crop-frame or 4/3 sensor, making the EOS M a full-frame camera will add to the bulk of the lenses as well as the camera, negating most of the advantages that mirrorless cameras have in the first place.
The RX 1 has simply taken a fixed lens and welded it onto a box with a sensor. And, like the EOS M, it has no viewfinder. The entire rig will have to be redesigned to allow it to be an interchangeable lens camera. It's already ridiculously expensive. Making it interchangeable will sky-rocket the cost. The RX 1 is a foolish model to emulate.