We currently do not observe the property aspects of the yovel year because, as I understand it, it's not practical until the ingathering of the exiles. (We don't own all the affected land now so we're not free to redistribute it.) Do we completely ignore it, or are there restrictions related to Levi'im and their historical cities that still apply? We know what at lesat some of their cities are and we know who at least some Levi'im are today. If I buy a house from a Levi in one of those cities today, is my purchase cancelled sometime within the next 49 years?
It's actually not so much because of practicality, but because the prerequisites for Yovel are that all Jews are living in the land of Israel, and each tribe in their designated territory. (So even if all of the land were under Jewish control, there's still the fact that almost no one knows what tribe they're from. See the discussion in the comments here.)
The rules about the reversion of fields, houses, etc., are dependent on Yovel, so they don't apply nowadays, even as in your scenario where we know that the seller is a Levi and the city is one of their cities.