I don't see this happening and here is why: There are still plenty of people that drive to the parks, which means that if you take a bus, security at most parks would still be required as there would be people that would have to pass through security, but to do so they would have use common walkways with those be dropped off by bus and other transportation, which means that you would have to go through security twice.
Personally, I think they should do more like Universal Studios Hollywood and have your bag go through an xRay machine while you go through the metal detector, for 95% of people they will just continue on, the other 5% would be the people that security needs to look at further for whatever reasons. This eliminates a lot of having security go through every pocket (like some of them do at
Disneyland especially, not sure about Disney World).