You really think this is about the busses? Enhanced mobility is a nice byproduct...
This is about the extra $50-100/night Disney will charge for the 7,500 hotel rooms serviced by this system. We're talking a half million dollars in extra revenue PER DAY. That's $180M per year. The whole system will cost WAY less than that... What a great investment AND it will help with mobility, add something cool to WDW, and on and on.
In addition, with 7,500 rooms (many of which are suites/villas) we are talking up to 30,000 people wanting to ride this thing around the same time.... Even 15,000 would be a crazy number to all want to get into 6 person gondolas at park opening or park closing. I haven't seen capacity numbers but I would be surprised if there aren't restrictions during (at least) peak times.