Actually, Evil Sakura, and Violent Ken aren't existent (as far as the Capcom official storyling goes). Ditto for the SF EX-only crews. However, Dark Sakura is probably going to happen sometime after SFA3.. maybe in a year or two. ^-^; And don't forget all of the other dolls:
Enero, Fevrier, Marz, Aprile, Satsuki, Santamu, Xiayu, Jianyu, Noembelu (from T. Hawks Tribe!), and Decapre. ^-^;

As I was talking about Zero (megaman zero series for GBA) and Violent Ken (SNK VS CAPCOM CHAOS) Here is how you unlock them.

Zero
Hold Start and press Up, Right, Right, Left, Left, Down, Up, Up, Up, Right, Then A, B, C, Or D

Violent Ken
Hold Start and press Up, Up, Down, Left, Left, Right, Left, Up, Then A, B, C, or D

Dark Sakura is pretty bad-ass in Mvs.C2