Given some of the entries in the Wal-Mart wave, it'd be nearly impossible for a lot of them to be repaints. The ones I'm most interested in, Age of Apolcaypse Sabretooth and Wolverine, would almost have to be done from scratch.
Let's face it, like it or not, Wal-Mart wields a LOT of power in the retail world, including toys. They want an exclusive wave with new figures, they probably get it, especially if they throw in something like a threat to not carry any Toy Biz merchandise if they don't.
The only recent incident I can recall where Wal-Mart didn't get something they wanted was a series of 3-3/4" G.I.Joe figures a couple of years ago. I don't recall the reasons offhand, but there was some sort of conflict between Hasbro and Wal-Mart. And really, who did it serve? Six figures that never saw the light of day (although they were manufactured to a fair degree and turned up in eBay auctions out of the Orient...)