Its been established Simpsons will be demolished when it closes. I bet Universal wants to move from from an almost 40 year old simulator clearly on it's last legs to a more dark ride like attraction.
Only time will tell what happens to Springfield and World Expo whether Pokemon takes it over it or not. Depending on what IP they settle on, it would not surprise me if those two areas get combined to make one huge area. with three attractions. One in the Simpsons plot, one that takes over FFL and MIB and one that goes in the plot where the spring tents are. MIB is a great ride but considering how Uni seemingly wants to move away from licensed IP to more in house stuff, It would not be a shock if it goes away eventually. But knowing Universal's recent track record, I am sure it's replacement will be great. And you have a modern day successor to MIB in MK at EU.