I don't have the link on me but Jim mentions in a Q&A Thor travels around COlleges playing College Football, much to Odin's chagrine.
So with that confirmation of where Thor is, the favoured theory that Donar Vadderung means Thunder YoungFather, isn't indicitave that Thor took over the Odin mantle. Siiigh. Alas it was a theory I enjoyed.
https://www.youtube.com/watch?v=Df_3c02lelg&feature=youtu.be
around the 12-13 minute mark.
It does seem more likely it was simply a hint that Vadderung = Odin, rather than a hint that Thor became Odin. Old Norse is a Germanic language. "Ung" is a suffix in German that typically turns verbs into a noun (e.g., erinnern "to remember," becomes Erinnerung "a memory.") "Vaddern" could be a verb that means "to sire a child." Thus, Vadderung would be a way to say "sire" or "father," and the name Donar Vadderung would just be Thor's sire. I have no idea where the "young" portion of that theory comes from.