I've always been for Mt. Crumpit over Lorax. Mt. Crumpit is perfect for the park--another large, visual icon that represents the biggest (or one of the biggest) Seuss character(s) out there (Grinch, along with The Cat in the Hat). Universal has their own castle with Hogwarts, and I say that it's time they build their own spectacular mountain.
Now don't get me wrong, I realize that the Lorax dark ride was critical in expanding the family offering, so I'd be all for another gripping family E-ticket dark ride located elsewhere in the park. As cool as the indoor JP Amber Mine coaster sounds, I wouldn't cry too much if they built something in replacement of it. And don't forget that Kong is supposedly coming...while a darker, more intense experience with giant apes/monsters, it will expand the family offerings of the park as well.
But yeah, I'm a Mt. Crumpit guy all the way! I REALLY hope it happens.