If you have reason to believe the migration will make no more progress, terminate it.
It is likely that a partially migrated account will be corrupt, but it is possible that it became stuck on an item that is inconsequential. If you have reason to believe the migrated account is corrupt, delete it, and start another migration. This time use a wired connection - either connect the two machines directly or though a wired LAN.
A wireless migration can take anywhere from acceptably fast (an hour or two) to days, depending on the many variables that affect wireless networking.