The net result is the same. If a portion of the MK guests are able to park hop to other parks throughout the day they will be replaced by portions of the other three parks capacity crossing over to MK. Ultimately at closing there could and likely still would be the same number of guests. Probably even a greater number as people would have been less likely to leave before closing if they hadn’t already spent the whole day there.
I'm betting park hopping will go the way of standby lines and fastpasses. The App will disincentive it.
Shorter park hours and more evening separate tickets will also contribute. Wouldn't be surprised if "two seatings" a day becomes the standard. Except for DAK. IMO.