They can't come back. Ever. There may be a few survivors out there but the entire race coming back is an impossibility.
Just the one
"Land that didn't belong to them"?
They settled peacefully in places that weren't occupied. And as a reward for their peaceful immigration, they were threatened with genocide by the Mer.
The Falmer tried to implement a genocide on the Nords in the name of Liebensraum - that's clear enough.
And the Nords turned the tables on them. Good for the Nords.
So genocide from one sides justifies genocide from another?
Also, the province belonged to snow elves all the same, I don't think the Nords would be to happy if a bunch of Altmer would suddenly start making new homes for themselves in some wilderness areas in Skyrim and claim it as a new land. There would be war there too.
Anyway I'm playing devils advocate here, and it doesn't really matter. I'm glad the Nords wiped out those bastards Falmer to be honest.