The important point here is that in general relativity, causal (dis)connection has only a global meaning, that is, over all of spacetime. It isn't something defined for a given instant in time, but over the whole history. Likewise, a horizon doesn't exist at a given moment; events that are on opposite sides of a hoizon were always, and will always be, disconnected causally. If the expansion slows down and reverses, bringing currently spatially distant point back together, then they were never disconnected in the first place.

The important point here is that in general relativity, causal (dis)connection has only a global meaning, that is, over all of spacetime. It isn't something defined for a given instant in time, but over the whole history. Likewise, a horizon doesn't exist at a given moment; events that are on opposite sides of a hoizon were always, and will always be, disconnected causally. If the expansion slows down and reverses, bringing currently spatially distant points back together, then they were never causally disconnected in the first place.