Current (mid-2012) consensus is that old questions should NOT be migrated.
See this answer for an excellent argument against migrating old questions because of the disruptive effect on the receiving community.
See also this official SE blog post which covers this issue:
Finally, be extremely reluctant to migrate old, answered questions. The votes and answers on these reflect the opinions and work of the community where they originated, and in most cases they’ll be somewhat out of place elsewhere – you want your greatest hits to reflect the best that your community has to offer, not someone else’s. And, again, the migration can come across as rude: if someone has invested serious effort into an answer and has linked to it on their blog or from their résumé, then snatching it from them without due consideration won’t endear them to you. Only migrate these questions when the alternative is deletion.
DO NOT MIGRATE OLD, ANSWERED QUESTIONS
LaTeX, I'm looking at you here.