I don't believe it for a second. For all their talk of their "homeland," Palestinians aren't going to emigrate to a hellhole where there is constant violence and no work. By and large the Pali diaspora lives in relative comfort in their new countries, exactly as the others should have done.
They'll go where they're "sent". Currently there are about 4,000,000 refugees per UNWRA. Only about 1,500,000 live in the West Bank and Gaza, 2,500,000 live in Jordan, Syria, and Lebanon, where they haven't been integrated into the local population. Those 2,500,000 could find themselves moving whether they like it or not. Again, that after a withdrawl, that isn't Israel's problem.