Have to agree with sam gordon on this one. I see Disney bringing in BAGS again. They would take the appropriately tagged bags from MCO to the resorts, pretty much the same as DME handlers did. Then, baggage is handled the same way it was with RAC when leaving WDW.
As far as the train goes? I'll believe it when I see it. DME stops on 12/31/2021. Brightline isn't supposed to be finished, in that area, until late 2023, which probably means sometime in 2024. And this is per Brightline's site! I'm not at all sure a train is a good, viable alternative to DME. We would probably see a train coming, and a train going, at all times.
Rental cars? Here's the thing. The vast majority of guests are not comfortable driving in WDW. I wasn't until about 6 years ago!! And that was after about 50+ trips. I finally started renting a car. I haven't used DME is a long time. So, what do I foresee happening? I see towncar services coming back, in force. I see Mears stepping up, probably contracting through Disney, to provide a discount service...just like they were doing prior to DME. I highly doubt that we are going to see a huge influx of rental cars...not at the prices that are currently being charged now, and adding daily resort parking to the mix.
I guess we shall see what happens. People got to WDW with little issue prior to DME, they will again.