Bricks, Masonry, Asphalt and Concrete - Crack in slab between rooms

A previous owner added a second (badly made) bathroom onto my house off the master bedroom. There is a crack in the slab between the master bedroom and the addition. I discovered the crack when I had the carpet replaced with Pergo in the master bedroom. The crack is right underneath the door between the bedroom and bath. It looks as though the slab for the addition was poured a little bit higher than the original foundation. When I pulled up part of the vinyl floor in the bathroom to see how far the crack went, the vinyl just peeled right off the concrete and it seemed pretty damp on the underside. I'd like to repair the crack for now, and then in a few years tear the addition down and put up a new, larger bathroom. I would very much appreciate any suggestions on how best to repair the crack. Or is this not the best plan?