I doubt Foley is replacing Don West seeing as one of the reasons Foley is upset with WWE is because of being on the broadcast team.
I would call TNA a rival, however I don't think Foley will be good for TNA in the long run seeing TNA's history of signing big name stars. I mean lets look at it. I mean who have been the major focuses for the last 2 years? Angle, Sting & Christian. Former WWE and or Legendary guys. Booker is the first big name star to come to TNA not to squash the home grown talent. (Samoa Joe) thats definatly a good sign, but take a guy like AJ Styles, who used to be the main event star, then has gone from goofy lacky of Christian & Angle and now were suposed to take him seriously as a major main event Face again? I've had a hard time buying it cause I still see the guy who wouldn't leave his bedroom while he tried to decide between Angle & Christian. And if Foley comes in, and if they actually have him compete, you know its going to be a main event spot. And with everything centering around Jarrett & Sting, is AJ really going to be a main event player? Are we really going to believe that AJ has a shot at being the World Champion again? I don't.