It could be the fact that Jurassic World could become its own trilogy, therefor they do not need to open JP expansion now and could do it in time. On a financial viewpoint, the Trek area at JP may have been expensive to maintain, especially since it always seemed empty. Kong in 2015 and Kidzone in 2016, if thats the case, sounds like a better plan IMO. It would make sense also. A new family coaster wont bring the masses to the park. two new islands in the form of skull island and a whole new concept to take the place of KZ both at HP scale and detail. that will bring in hordes of tourist and give Comcast more of a reason to keep investing into the parks.
Here is my guess as to what we will see (with the information we have so far)
2015 - Kong, KZ construction, Citywalk Expansion, Hotel 5 construction - And we find out whether or not Uni has more land that they have been keeping a secret, or they will buy land for more hotels
2016 - KZ finished, Citywalk Expansions, Hotel 5 Done, construction begins for waterpark & transportation system between Current property and new water park area
2017 - Waterpark Opens
I think JP is a proof that we plans change at any moment. For all we know the expansion could still be going on