With how Shrek is featured on banners and the digital LED displays on the outskirts of the resort, I would hope Universal is considering or knows the IP deserves more justice then just a play set and basic area in Dreamworks land. Simpsons's plot isn't big enough for a fully immersive land, but something like an expanded Shrek presence could fit the bill.
To me Wicked if comes to UOR it's Epic or bust if you want to make it as immersive as it can (and should be) to do the IP justice. The Springfield plot just doesn't cut it. If they are other factors holding them back, wait it out to do it right in Epic.