Hi - I am slightly concerned that when moshiach comes I will need to give my house to its original tribal owners? Efraim.
Firstly, to buy a house anywhere in Eretz Yisrael is such a great mitzvah m’d’oraita that if need be, it even supersedes Shabbat (Gittin 8a), so you definitely should do so! How much more so today when the nation of Israel is BH systematically coming home from all of the exiles to nationally re-inherit the Holy Land! Technically, there’s a difference of opinion among the tana’im whether all of the ten tribes will ever return or not (Sifra, Bchukotai 81). Being that we’ve been searching all over the world for many years, and have barely found any, and there are no unknown continents left to surprise us, it seems that the pessimistic (or for you, maybe the optimistic!) view is turning out to be correct. Even if in they end they do return, and fulfill all of the requirements necessary, we find in the Tanach that members of other tribes lived among the respective tribes (Radak). In addition, I have no doubt whatsoever that should all this be realized, the Sanhedrin will then figure out how to justly reimburse or re-locate everyone, if need be. The Torah is a Living Torah, which means that not only is it practical and “do-able”, but it’s eternally idealistic and beneficial. Especially when you take into account that we’ll all be in the same situation! “Diracheha darchei noam”, all of her ways are pleasantly sweet and ways of peace.