The SL1 and "M" are totally different cameras. When the M2 arrives, it may be just a minor upgrade. At some later point, there is supposedly going to be a enthusiast mirrorless with more professional features. Don't bet on it, it may be all ready to go, and never actually released due to market conditions.
If you need a camera, get one, if you really don't have to have one, I'd hold off. I've been holding off for over a year, waiting for something that would make me want to upgrade my old 40D. I've had a couple of 7D's and have FF bodies, but keep going back to the 40D as a backup. I bought my wife a 1G X, its fine, I ended up paying very little for it after the rebates last fall, so its a freebie.
I am really not expecting to see a crop body that is advanced enough to make me jump.