From everything I have heard (CM's have started to ride the unfinished version), it should be a solid C-ticket attraction.
I'm glad Disney is adding this. Not only does DCA need more things to do, it needs more family things to do. The rethemeing of the area and finally doing something with Limo is a step in the right direction. As noted, there is still space available in that area...
Oh, and I just thought I should mention that not every attraction can be an E-ticket. You guys try asking the board for $100+ million dollars for a new ride every year when you're park has performed well below initial expectation since it has opened and see how far you get.