Now that we can migrate off topic questions, what sort of migration paths should be useful to have?

I think that adding at least [Cross Validated](https://stats.stackexchange.com/), if not one or two of the other science sites, would be reasonable. 

(Note that [there is a two months limit](https://meta.stackexchange.com/questions/151890/disable-migration-for-questions-older-than-60-days) on migration. We won't be able to migrate posts older than two months.)