I hope Nintendo doesn't get greedy and requires re-purchasing VC games.
Honestly, I think they might lose more money that way. There are still dozens of VC games I want to buy (especially if they add GCN games), but if my old titles don't transfer I'm not going to have any confidence in the service and probably won't buy anything at all if I don't think they'll last past the Wii U.
(...Well, I might buy the occasional classic, but I certainly won't go crazy like I did with the Wii VC, and I'm definitely not going to re-buy any Wii VC game I already bought.)