It's possible that One Piece or some other lesser known property (D&D, etc) could replace LC if they have a really favorable merchandise split, less creative demands, and take a smaller percentage (if any) of the ticket price.
Let's say Universal's deal with The Pokemon Company (or Zelda, LotR, etc.) gives Universal 5% of the revenue from any merchandise sold in the park. If they strike a more favorable deal with One Piece, for let's say 15% of merchandise revenue, then Universal earns as much money selling a single One Piece shirt as they would from selling three Pokemon shirts.
We also have to consider that assuming Pokemon increases attendance, that increase would have to be large enough to offset whatever percentage of the ticket price Universal gives to the Pokemon Company.
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Basically I could see Universal going with a cheap and quick license over a mega property *shrug*