Some notes about how this will play out once we go further. Alenanno notes what's relevant for us at the moment since we're in private beta - no migration, period.
Once we enter public beta, the main method to migrate will be to flag a post for moderator attention. Then, someone on the community team, or your pro tem moderator team when that shows up, will handle the rest. In this vein, any kind of migration is fine if it works, we don't need concrete paths.
If this site reaches graduation, then we can open official migration paths that even normal users will be able to use when voting to close. However, the requirements to this are strict. We need a demonstrated need of the migration path as illustrated by a history of migration. That is, we don't just add a migration path based on logical connection. Consider Arqade, our Gaming site, and our Game Development site. In logic, they would make sense to migrate to each other. In practice, there is no history of migration from Game Dev over to Arqade, and there have been only less than 30 questions migrated from Arqade to Game Dev over the course of over 2 years. So there isn't enough "wrong traffic" to warrant the official public path to be established, it's unnecessary.
Let's wait and see what migration trends we see as the coming months go by, then we can revisit this topic.