Well, it would probably depend on how sales of Secret Six are doing. If they think Simone would do better on JLA, and Secret Six wasn't selling well, then we probably wouldn't be seeing much more of Secret Six. However, I think (?) sales are doing well enough that we don't have to worry there.
If sales were doing well, though, that would mean that she was split between three (?) monthlies (she's working on Secret Six and Wonder Woman for sure).