I see where you are coming from, because it makes sense that they would break up eventually. However, it would feel cheap because their ending together was very concrete in RotJ. It's an "And they lived happily ever after" type deal. The other major problem with this is that this is not Han or Leia's story. An unecessary subplot about how they split up after Jedi would just get in the way of building momentum for the new story. Again, you bring up real life. In the context of Star Wars, a high space fantasy, building realistic romantic relationships is not that big of a deal. Han Solo has already had his redemption arc. Setting him up as a loner again only regresses his character. The original three (Han, Luke, Leia) aren't the main characters of the story anymore. I wouldn't have as much of a problem with this if they were. But in my mind, Episode VII should be about building new characters, not re-examining old ones.