I can tell you that while I was in the parks last week, there was very little physical distancing going on, even with it officially at 6'. Enough people just aren't doing it - in queues, in merch lines and stores, walking around, anywhere - that most of the time, I was within 6' of other people. So I don't really think a an official reduction is going to feel terribly different.
But what it might look like is physically shorter ride queues (same wait time, less distance covered), and closer seating/standing for shows. My best guess is that they'll go to 3' outdoors and retain 6' indoors. In a bigger picture, reduced distancing might mean being able to put more staff in places like kitchens, which might mean more menu items and/or more restaurants open. It'll be interesting to see just how it shakes out!