Well we don't know IF Shane was the father or not.

It may not even come up again in the series and that wouldn't bother me. However, I can maybe see writers pursuing that storyline more than the "Ghost Lori" scenes. I took the phone calls Rick got, and now the Lori ghost, as Rick's therapy. He'll come to his senses (soon I hope) and move on. I hope that storyline fades because I think it's unnecessary don't you?
TIS