Based on the amount of placeholder data we noticed earlier on in the generation, I won't be surprised if there's NOT a Dawn form for Lycanroc. While it would make logical sense based on the name and the fact that we have a complex time system with multiple phases, it wouldn't be the first time Game Freak has seemingly left something out or failed to complete a circle of sorts. Just as an example, all the types that were originally special have an eeveelution - except Dragon.
However, based on that same placeholder data, I think it's pretty likely that we'll get a new Mimikyu form. But what could it be? It's lore establishes its immense jealousy of Pikachu being the basis for the disguise in the first place - so if it's based on another Pok?mon, it has to be something really popular. Could it be its "true" form instead, with a different ability? Maybe even differently distributed stats?