My personal opinion is that we've always had the worst version of Rivers, the Island, and the train. So I personally don't care what they do as long as it's better than what was there before. I'd also add it's not like we're losing River's just for Cars rather we're losing it mainly for Villains and just the bottom part for Cars.
Really hopeful that we finally get new scenes and upgrades for the train, especially when it goes through the Villains area. And I'd ad the DAK river boat as well as the Swan Boats the use to exist for MK we're good ideas for moving guests around but it's the same issue of ride capacity and do you get moved quicker walking it vs taking the boat. That's one reason the train's been so useful because it moves people quicker then walking and the lines are usually not bad. You can't argue that with the DAK boat and it's not like it has the scenery of Peoplemover sadly.