I have been talking to John Myhre, Production Designer of this movie, who is a personal friend (and he has a great resume, with 2 Oscars and 3 other nominations). He said Disney recognized the weaknesses of the third movie and brought in Rob Marshall (who John has worked with multiple times) to re-invent and revitalize this franchise.
He just called and said that they just had the preview for the top Disney execs and that they thought it was sensational, so I am really looking forward to this!
Bruce