Are there any reasons why you would avoid going disc (other than cost) for racing cyclo cross?
One good reason to stick with cantilever is easier wheel swaps. Last weekend races, my son flatted and we did not put spare wheels in the pits. Neutral support had spare wheels and if my son had a disc based bike he would not of been able to use them. Even if neutral support had disc wheels, with differences in rotor size they may not work for your bike.

Full Disclosure: my next CX will be disc based, I've been through too many rims with brake surface getting dished from grit and grime.