I agree that Osha is a good caretaker and will try to be as nurturing as she can under the circumstances but even so Rickon will have grown up without a home and a family. He will be different. Not saying it will be necessarily a bad thing but
it is just a fact of his life. He will probably be more wildling-like since he will have been raised by one. He is 5 so in the coming years he won't really remember much about his prior life in Winterfell.
I didn't think of that. They do think Bran is dead and gone so naturally Rickon would be next in line.
Still at this point to find him would be pretty hard. He is in the north which is not exactly a small place so the
likelihood of him being found and set up as a puppet lord is pretty slim in my opinion.