Ron Gilbert doesn't own the rights to Maniac Mansion or Monkey Island, and he seems busy pitching his own (RPG) game to publishers.
But I do agree that LucasArts is just recycling the same old same old. Companies like Telltale, that dare to make cool adventure games, may attract the attention of other companies, who in turn may think "hmm... why aren't more people making adventure games?" It would be nice if LucasArts would be one of those companies, but I wouldn't count on it. At least there's always Telltale!