Has it been confirmed that additional vans or buses will be used that aren't being used in the normal transportation flow? In other words, fewer people on your bus might not mean much if there are fewer buses.
At this point that part is
all speculation. Nobody knows if the "pixie-dusters" or the "doom-and-gloomers" are right, in their outlook.
I imagine the truth will be hard to figure out since the intricate details of Disney bus scheduling aren't something most (any?) of us have any insight into.
If they take from the existing pool of busses and drivers, the regular bus situation will suck but that's how a lot of people already feel about it so likely, it won't be noticeable and my guess is that if they add to this option, unless a
whole lot of people use it, the impact won't be great enough to be noticeable, either.
Basically, I think if you're unhappy with the current bus situation, you'll continue to remain unhappy, regardless, unless you choose the add-on.
It seems, not everyone is unhappy with the current situation, though.
I drive, which is a bad option for Disney as I take up parking spaces all over the place and leave random spots in full lots when i leave, add to the costs of parking booth attendants, parking "arm waivers" and courtesy trams when I park hop but none of these options is enticing me to consider Disney transportation as my alternative.