Nothing has been confirmed about the pokewalker as far as I know. But there probably won't be one - it was a special thing for heartgold/soulsilver.
As for pokemon following you, all the gameplay footage released so far doesn't have a pokemon by your side, so again it's unlikely they'll do that. Remember, they had Pikachu follow you in Pokemon Yellow, then dumped that idea until HG/SS.
See http://www.youtube.com/watch?v=pjqEfHzXfWs for some gameplay footage.