Ah, but that’s the magic question… if there can be said to be a cardinal rule of Jewish marriage law, it’s that a woman cannot be married to two men at the same time. Saying that she can have two husbands at the same time is such a major chiddush (and that’s a huge understatement) that you need to have *really* good sources to allow it.
Practically, she can’t. Halachicly, she might be able to. See the gemaros I quoted (They are NOT Halacha, but the concept does exist). Delve into why the “rule” is true, and there are halachic loopholes that can around it.
(There is a Chakirah as per why an Eishes Ish can not get married to another individual. IIRC, The s’ddadim are Kinyan and Ervah, neither which apply if the husband dies (although there is a sa’ad to say the kinyan still exists in some respect, but it becomes non-exclusive, due to Missah being a Matir on a Gezaras HaKasuv level)).
What will happen when Moshiach arrives, I have no clue. I’m only discussing the lomdish aspects of the question.