I think there are four camps of people:
1) They hate the eradication of RoA, TSI and the Riverboat
2) They hate the Cars IP being used at MK and specifically there
3) They hate both notions.
4) They are open to change
I'd put myself in #4, but with the caveat, they have to execute properly.
Like some have suggested, it sounds like Disney is committed to removing the Rivers for several reasons (costs to maintain #1)
They can't exactly put massive showbuildings in this space. For the record, Cars wouldn't be my first IP either. I don't know what they could have used.
I'm trying to remain open minded to wait to see the end results. If they can pull off the aesthetics and good attractions that draw more guests than TSI/Riverboat, it can be a net win.
They have to avoid a huge swing and miss. They can't screw this up. Nobody will forgive them for destroying RoA if it's not worth it.