I realize that this is about Disney World. I moved to Kissimmee from Orange County, CA, a couple of years ago, and the differences still occasionally blows me away. Like I said, "Bizarro Land."
To my knowledge, Disneyland has never offered evening only admission. I'm not sure what the point would be without major changes in guest attendance patterns and entertainment times.
It's ironic, because I think Disney originally started offering nighttime entertainment to keep people in the parks later. But it worked too well. Disneyland became a "locals park", and passholders would go there whenever they had a few free hours to just "hang out." Watching the entertainment became a nightly thing. You'd see the same groups, in the same spots, night after night.
There is probably no equivalent to that dominant "locals" subculture out here. And that's a good thing, because it allows Disney to offer after work only admissions to locals.
We also have EPCOT, which is massive, a fantastic dinner dining destination and has a vast area with excellent entertainment viewing. California Adventure sort of plays that role in CA, and if they ever did offer evening only admission, that's mostly where it would be, but it is nowhere near the scale of EPCOT.
If Passholders get blocked more from all day admission, that's a pity. But it still blows me away that Disney World will actually make nighttime entertainment more accessible to passholders. Again, as someone from California, you cannot imagine how wonderful that is from my perspective, and how lucky we are to be in Orlando.