IOA is pretty massive and just imagine how much "bigger" it will feel when you don't have a large pond in the center. I really appreciate Alicia's overlay of IOA over the FW area in her video earlier this month.
But as large and far into the future as FW may be, put me squarely in the pro #4 camp (as long as the current tourism growth/trend continues). Something I feel Universal does very well is pair IOA and USF together; they complement one another extraordinarily well. It's a huge competitive advantage over Disney, where at Disney it's difficult to move from one park to another (and never mind getting back to your car you parked at Epcot when you're at Animal Kingdom). Compare this to Universal where it's a ~5 minute walk. I feel like it's a huge advantage that would be not be realized with FW sitting by its lonesome.