Currently, if I flag a question as off-topic, I only have the option to recommend it goes to meta DB.
Will I ever be able to flag it as more appropriate for ServerFault or SO?
One day, in the near future, migration paths will be assigned by the dev team. As a matter of fact, we might even be on the receiving end of a migration path from another stack. But for today, you pretty much just need to flag for a moderator if you want it migrated out. Additionally, we generally try and counsel with the other site when migration paths haven't been defined to ensure that it's on-target on the remote site.
They often are by that point, but we like to make sure.