No way. I don't want a 12" Surface to be limited to Core M. I love the 12" of my Surface Pro 3, 14" would be way too big for me, and I just want a non-M Skylake CPU in it. Skylake Core M would be slower than the Core i5 in my current SP3 I think.
In an anandtech test they found the zenbook ux305 (lowest broadwell core m) to keep up well with an i5-4200u for day to day usage, as it almost never throttled due to heat. The skylake core m chips are supposed to be a decent step up from that too. A core m surface pro would still be decently fast I think.