Mr. Anthony,
If this tree were mine I would definately wait until spring...The reason for my opinion is by waiting until then you still have a good chance of success with the air layer...Even if it has not made visible roots, chances are very good that it has at least formed the callous needed for rooting...If you make the separation in the early part of spring and then pot up your air layer it will be like a cutting with a great head start...Although I have never tried this with a maple layer, I have successfully rooted other trees by separating a layer in the spring with no apparent roots...
Best of luck whatever your decision, and let us know if you choose to try this and it works for you...
Regards
Behr
