but I doubt people are going to be thrilled at having to buy another full set of models they already have to get the new cards.
No one is going to buy their whole collection again just for the the sake of upgraded cards. The only way X-Wing 2.0 could work, is by selling the cards separately, I can't imagine anyone sticking with the game otherwise.
At least with other games like 40k, FoW, Warmachine, the models are always useful because you can just buy the new codex/book/card pack, and you're done.