Thats not necessarily how it works though. Disney can also sell Marvel merchandise. The thing about people buying it at IOA is that that means those people are at IOA and not Disney...meaning whatever Disney gains from Marvel sales, they lose in stuff like Frozen merch, Mickey Mouse balloons, even food & beverage. So its not exactly a cut and dry win-win situation. And by 2050 (assuming another contract is not created or the rules of the deal change), B&M flying coasters could be obsolete, as could the popularity of Marvel.
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Thanks for clearing this up, I thought I had seen somewhere that IOA couldnt do much more than improve existing stuff at MSHI. Looks like Disney is a little more than just a pebble...