...Or Discovery Island, Image Works, Food Rocks, etc...
I would think the idea to reuse WoL would come from a budget reason, crowd and speed reason...Im guess that if anything is going to go into WoL it would cost far less and would be far faster to reuse the building. The business guy in me thinks that IF something is going to go into WoL, they would likely want to get proper construction started by this winter, if they want to hit an opening date that would match up with GotG to siphon off some of the lines.
Logic tells me that anything going into that building would be pretty tame, low cost and extremely family friendly to balance off the three thrill rides on that side of the park...all things that could be accomplished quickly and with low cost.
Im not going to even guess at theme, but "business me" cant see anything amazing going in here, from an attraction standpoint.