For those who do not visit Meta.StackOverflow regularly, there is a recent change in software on how Question Migrations are handled.
In particular: we can no longer migrate questions older than 60-days old. The only case to be made for migrating older questions is if a newly graduated site now better covers the subject area which previously fell under our scope. (For example, think of when Mathematica.SE or SciComp.SE came into being.) In that case the questions have to be both requested by the receiving site and also proposed by the giving site. (See the above links for details.)
How does this change how we handle questions on this site?
Not much, fortunately. We have always been fairly permissive about what falls under Mathematics (see our FAQ). The main impact that I foresee is that occasionally we would see migration requests for old questions that remained on this site for a while unanswered, and now has probably a better home. Previously we would just deal with them silently. But now we would have to follow the procedure above.