OH dear. It's a case to case basis, really. Not that I'm closing all doors of possibilities on my previous relationship with someone, but seriously, why would you do that to your ex? I mean, if either of you dumps each other, aren't you drawing demarcation lines on your relationships -where it'll end ends there? It's a question of initiative. If someone still loves the other, one will eventually find a way. You don't really have to burden yourself with the effort of reading your ex's mind. Just let it be.