See this blog post from Jeff. I suggest we need to allow migration to StackOverflow (the programming questions) and math.stackexchange (the more mathematical questions). What other migration paths do we need?
Computation Science? There's certainly some overlap of subject matter with CrossValidated. It's still in beta, and needs more questions if it's ever to get past beta. I'm not clear if migration to/from beta sites is allowed.
Looking further ahead, we should consider adding Quantitative Finance if and when it comes out of beta (currently still in the 'commit' phase).
To tex.SE? A lot less common than math.SE or StackOverflow, but seems worth considering to me. Example: Typographic conventions for width of figures in LaTeX data analysis reports Reverse path probably not needed.
Didn't find this discussion anywhere else in meta, so I'd like to add that we should allow migration to https://datascience.stackexchange.com/.