When they open up, if you control an exit point then your realm gets to emigrate first
Actually this is an interesting idea for making a continent closure more fun. Suppose you set a time limit and claim the island is being destroyed by a series of storms and earthquakes. The storms make the oceans near impossible to traverse except for a few key sea lanes. Each lane will only lead to one other game world. If you don't exit by one of these lanes in time you will end up adrift in the storm wracked sea and wash up on some random continent.
This encourages realms to leave the continent in an organized fashion and it can make things interesting in other game worlds as swarms of foreign refugees show up, potentially disrupting their status quo.
