Assuming we will, at some point, be reunited with some or all of the exiled Ten Tribes of Israel, will we expect them to celebrate holidays that are specifically Judaic in nature, by which I mean that they are commemorations of events that happened to Judah as opposed to the other tribes?
I am obviously referring to the holidays of Chanukkah and Purim. Should the Ten Tribes celebrate such holidays?
On the one hand, these are well-established holidays in Jewish tradition and law, and would we want a large portion of Jews (Judah) to be celebrating such days while the rest of Israel does not?
But on the other hand, why should they have any reason to celebrate? Perhaps we should treat this the same as any other customs that arise within communities in exile (i.e. inserted prayers like Yekum Purkan and Av HaRachamim etc.), which the individual communities observe and others communities have no reason to accept. If one of the Ten Tribes with whom we will be united, for example, has accumulated one or two holidays in commemoration of events that occurred in their exile, would we be expected to observe them?