The thing I have to wonder about, though: why? What benefit does KI get from opening two weeks later than what they used to? I don't mean to whine, but the earlier opening days weren't completely empty--I've seen slower days on Haunt Fridays--so I don't think they were totally losing money a couple years ago. (Not that I'm privy to those facts... For all I know, those days were prone to attracting only passholders who wouldn't buy anything, so the park could have been losing money hand over fist.)
It's been mentioned before on here that Paramount's season pass preview days helped train employees and iron out ride kinks prior to the real opening day. The old April weekends could almost be considered a substitute for that--they weren't packed, but they had enough people there that the park was running well by May/the start of daily operations. Maybe it was sheer coincidence, but 2011's opening day seemed pretty hiccup-y. Rides were down left and right, with relatively full queues of people who I personally witnessed complaining a lot. But I'm just speculating.