Every fairtax proponent I know of endorses getting rid of the 16th amendment. In fact, the fairtax bill itself endorses the idea. But if you think that they are going to repeal it without the replacement tax system in place first - well I've heard of a bridge in Brooklyn that someone is trying to sell.
Once the Fairtax is in place, repeal of the 16th will be a relatively simple matter as millions upon millions would demand it!
I agree, and I know that every proponent of the Fair Tax endorses repeal of the XVI Amendment. But the part that worries me is that in order to repeal the Amendment we will have to go through the Constitutional amendment process. That is up to the state legislatures and I worry that 1/4, plus 1, of the legislatures will not approve a repeal amendment. Still, that would not stop me from supporting the Fair Tax and I would hope any enabling legislation from Congress would make the Fair Tax contingent on the repeal of the XVI Amendment.