Those aren't the only options. It's a total bus system with hundreds of busses operating in a complete system across all destinations, not independent distinct systems for each route. They can, and already do, all throughout the day change what route a bus is on all the time. It's easy to see anytime a trip from a resort to a park drops you off at a stop that isn't for the resort you came from. That bus just changed to a different loop.
Viewed in isolation of just these resorts, if every bus loop was dedicated. They would need to reserve mostly useless extra busses in case it shuts down. With enough capacity for some basic, probably poor, level of wait time. But, this is the wrong view.
Viewed as a total integrated system, busses are pulled off other loops and redirected. This increases the wait time on those loops that have less busses now. However, the goal would likely be to make that increase small by spreading it around as much as possible. Creating service to replace the missing item, at some basic acceptable wait time.
Adding the new gondola service and eliminating the bus service loops it replaces also done't actually mean they have to eliminate actual busses. It could be that all those actual busses and current drivers are redeployed someplace else in the overall system. Providing better service for the rest of the overall bus system. It could mean not expanding the bus system with additional capacity. This is sort of like eliminating actual busses, by this system meaning they don't need to buy more busses to increase capacity throughout the system. Kind of a "was going to buy more busses next year but don't have to now, so it's a reduction". It's a little twisted logic. It could also mean that they take busses off the road completely, but it's definitely not the only option.
They already do this all day long as capacity needs between different destinations changes throughout the day. In this way, the bus system is actually much more flexible for dealing with capacity changes throughout the day. It's that the actual bus service experience vs a continuous operation system is so much worse. Made worse by the actual road infrastructure those busses rely on being worse and subject to congestion. Part of the capacity changes throughout the day can be traced back to not just the number of people needing a route but also the time a route takes. That's another huge advantage of the gondola system, it's transit times should be significantly more consistent.
