If you're doing it right, your registrar doesn't run your DNS, so there's no DNS migration. Of course, if your registrar is also doing DNS, email, and web hosting for you, it's messy.

For this poster, I don't think they can migrate to a different registrar while their domain is in the 'redemption' period, and they may not be able to migrate within some time period (30 days?) of renewal, either.