I think I'm a Celeb benefits two sorts of person (a) those that have been forgotten about a little and need their career revived (The Vernon), (b) those that are very talented and just need a little more exposure to take their career to the next level (The Jordan).
Unless somebody acts like an idiot, it can generally only be a good thing.
For Dean - as others have said, I am sure it can boost his "talking head" / "panellist" profile. Radio wise who knows, I can't really see him ever getting much promotion at Radio 1 again. That's not to say he might not get another 5 years at the station in his current slot or weekend slots. But it'd be pretty rare for anybody to get a big daytime slot, get demoted out of it and come back.