We should not worry about ratings. While its numbers aren't the best they have been, OUAT is still strong at its level with other shows. OUAT is a very developed show, and ABC would probably be boycotted if OUAT were suddenly cancelled. I don't know what more the writers can do with OUAT to make a huge final season, so I'm assuming that the sixth season will be its last, but we WILL know beforehand. They wouldn't do that to us.
I wonder what happened to Lancelot when he went to visit his mother--I'm really curious about it. I hope that Merida stays on the show because, if she doesn't, she'll be yet another pointless character who contributes nothing to the main storyline. And I'm ready for something interesting to happen to Snow and Charming rather than a simple fight resolved seconds later.