Logistically, if IOA gets more, it won't be until after the first batch of Nintendo content hits IOA (and after Gate IV opens), in what I presume is now the 1.5 expansion of Super Nintendo World for the entire resort that was previously talked about.
Honestly, I see Zelda at IOA and Pokemon for Gate IV..due to one reason.
Pokemon, is Pokemon. It's one of the most iconic gaming franchises out there, and that it will bring a very different crowd than those who are coming for Mario or Zelda. It can very easily be a landmark land for the fourth gate, and a headlining aspect of UOSouth in a way that Hogsmeade pushed IOA.