Those might come across as slightly out-of-place, if X/Y are much to go by, and in addition would usually have to be 2D. While they could make the games in 2D or 3D, they would generally speaking be promoting 3D, and other modes might seem to get in the way if the 3D were seen as important in some manner. Usually, the locations and so on are very different, and might come across as slightly comical with the older sprites, especially as the older games are more identified with the series in pop culture and elsewhere, unless they wanted to be like Sonic and have it only be partially seen. That might just make the contrast clearer, though.