I'm going to be massively shocked if Disney takes any significant steps to change their current process in any way. Or gets this right 100% of the time. Even for stays booked after 3/21.
They will start with seeing who is arriving via ME, and who isn't.
MDE tells them that.
Folks who arrive via ME and rent a car later may well fall through the cracks. Would not surprise me one bit, would it any of you?
That leaves those who's MDE don't show they are arriving via ME. They are going to assume that they are arriving via car that is going to be parked on property. And most of those guests probably are arriving via a car they are parking on property. I would not be one bit surprised to see them automatically add parking to all of these guests, would any of you?
But there will be those like us, who use car services, Uber, Yak, etc. These guests may well have to verbally tell Disney not to charge them for parking. This is actually what I anticipate I will need to do during our April stay, even though we booked before 3/21
ETA - I don't believe there will be any action or changes done in the parking lots, at the security gates to enter or exit the resorts either. I stand to be wrong but that's what I think is going to happen