Developmental disabilities is a pretty big umbrella.
The current system was actually put into place in 2013. The changes that were made several years ago only really changed 3 things - the ability to do advance video registration and the addition of 2
DAS Advance Selections in connection with doing the video registration and guests being able to make DAS Return Times on the app instead of going to attractions to do it.
I PERSONALLY would not like a medical documentation system - especially not like the third party Universal is using. It has its own set of issues and ways it can be abused
Registration at WDW will be ahead of time by video chat the same as now. From what I've read, staff IN the parks won't be doing DAS registration, but it will still be available via a video chat with the Accessibility Group on a Guest Relations tablet in the park.
Not sure how that will actually work, but an in park option will be available, just not in person