It seems that morph will appear throughout the whole block (but with some changes), according to what Mark Rosewater wrote in today's article on the Wizards site:
MaRo wrote:Morph in Khans of Tarkir wanted to be morph pretty much as you know it. There are a few tweaks and couple of new things, but we wanted to start out the block with the morph players already knew and loved. Let me stress, though, that as with the wedge theme, morph is going to go through some changes in this block, and not necessarily in the way many of you might expect. Most of that talk, though, is going to have to wait for Fate Reforged and "Louie."
Now, the questions are: can we expect an expansion for DotP2015? And if so, will it be based off one of the expansions of this block? And if so, will the developers decide to build support for morph? If the answer to all those questions is "yes", we will be very sorry (even more than now) that we can't mod DotP2015.