Most likely WDW’s contract with Mears had a one-year out and prohibits Disney from establishing a similar service for a defined period of time. I’d be surprised if Disney doesn’t offer an up-charge ride and/or luggage delivery service when they are able.
This is almost certainly the reason for the termination this early and the lack of a proposed replacement (which typically can be revoked if Mears and Disney come back to the table). We obviously don't know what the state of negotiations or whether this could push Mears to cave on some of Disney's demands, but it's still possible they could still come to a new agreement. If that doesn't happen, I agree that a non-compete clause/ROFO situation probably prevents Disney from even vaguely promising some kind of replacement.
One thing I do know for sure is that this is very much NOT a cost-cutting measure as many on here are saying. While Disney has probably been losing money on DME since reopening during COVID, DME almost certainly paid for itself prior to COVID and there's no reason to think it wouldn't do so once COVID is under control. First, DVC owners probably paid most if not all of their share of DME costs in the form of annual dues (and while no DVC owner is the same, Disney certainly has the ability to figure out a number that worked in the aggregate). Second, most guests valued DME more than it actually cost Disney on per guest basis (while the free transportation meant some cost savings, those savings were never anywhere near the savings of staying off-site and paying for transportation out-of-pocket v. staying on-site with free DME), which made it easier to jack up the prices of the resorts. Finally, as many have noted, DME significantly aided Disney's efforts to keep on-site guests spending their money within the Disney bubble as long as possible.
I want to be clear that I'm not some wide-eyed Disney defender who believes they can do no wrong. You only have to look at the insane inflation in on-site prices (most Deluxes cost close to or more than the Four Seasons, despite coming nowhere close to them on a pure quality basis) over the last few years, while simultaneously not adding any new perks/taking perks away, to realize that Disney wants to squeeze every dollar it can out of its guests. That's just not what is happening here, for the reasons I laid out above and more. Either Disney is playing hardball with Mears/doesn't want to get locked into another 20 year contract with them or they have some other replacement in mind, because it wouldn't make sense for them to cut DME for financial reasons when it probably makes them more money than it costs.
Finally, the Brightline railroad (should it ever happen) is unlikely to be a viable replacement for DME and I doubt that Disney or the Brightline views it as such. The Brightline is a commuter rail line targeted at Florida residents who want an alternative means of transport on the Miami-Orlando-Tampa corridor than driving/flying. The only reason a stop at WDW is even considered is that its already sort of on the way from MCO to Tampa and there probably would be a decent market from Miami-Tampa residents choosing to take a train to WDW instead of driving or flying. Brightline is not going to try to be a shuttle line between WDW and MCO.
