LOTR probably won't happen since Nintendo, Potter, the Classic Monsters, DreamWorks, JW, BTTF, Jaws and original concepts give them plenty to go off of.
Doctor Who would actually be great as part of a continuation for London. It provides a nice transition between Diagon (London setting, blends fantasy/reality) and MIB (time travel, Daleks, Cybermen). It would be very successful - maybe a ToT-esque E?
Doctor Who and Sherlock would be a much better use of the Fear Factor area IMO.