I think the 8 SF2 characters on the initial roster are enough to hold over people. It isn't like they're not coming. I'm sure a lot of people mained Ibuki and Juri in SF4, certainly more than someone like Balrog and they're just as eager. Urien and Alex should have priority.
Yeah but Ibuki and Juri have play styles already represented in the game, where Guile and Balrog are mainstay archetypes. Balrog > Juri > Guile > Ibuki would be okay for order.
Personally I'd like Urien > Guile > Boxer > Ibuki > Alex > (Juri's replacement)