I genuinely can't imagine them entering into a relationship without first, um, working out their issues. Which means a psychological struggle of titanic proportions. If not for the fact that Snape was trapped and couldn't get away, Harry would never have learned that Snape felt anything for him other than hatred, which he already knew.
I think the fire did more than just burn away magic. It burned away their debts and their need to deny each other. But I hope readers don't begrudge Snape the need to be free of Harry for a while. Don't worry, Harry will certainly follow. Give a Gryffindor an inch and they'll take ten thousand miles. :)