Things just got more interesting with this reveal of the Z-Move interface. It's even bigger than the Mega button was, and since it's oddly shaped at the bottom that probably means the new Mega button will be relegated to the remaining space below it. At least, I assume the Mega button will appear in a different space than the Z-Move button, or else Rayquaza wouldn't be able to Mega Evolve while using a Z-Move.
Another detail this demo revealed is that Pikachu's use of the Normal Z-Move actually used Slam's PP, which just opens up more questions. If Slam had 0 PP for whatever reason before you decided to use your Z-Move, would it even work? If Pikachu knew a special Normal move in addition to Slam, would they both appear as this Hyper Sprint thing or does the base move category matter? If it were holding an Electric Z-Crystal instead would Thunder Wave be usable as the base? Plenty of possibilities here!