Considering the endless fan requests for Pokemon fusion, I could see Gamefreak fulfilling it indirectly with a twist. Imagine a region where the Pokemon researchers notice that the Pokemon there have certain features of other discovered pokemon. This water starter could be the posterchild for the most obvious "fusion" while other pokemon in the reigion would have only a few subtle aspects taken from existing pokemon. It would be too cliche and obvious to do direct fusions. Having a region where historically Pokemon adapted some of their features from thousands of years of interbreeding would be a bit more original. It would also prevent players from expecting the ability to choose which pokemon to fuse together and completely relieve them of the great technical work involved in a real fusion system. This would well work together with games named Plus and Minus where the main gimmick would likely be augmenting pokemon in other ways, maybe something like adding or removing types from them to augment their strengths and weaknesses.
