The first Cutscene takes place after world 1, meeting Yoshi. Luigi does not come in until World 2-2, and you can skip him and encounter him for the first time in another level.
The second Cutscene takes place after World 5, Bowser has a golden star locked in his dungeon and Mario must fight him to win it, but is this the end of Bowser's appearances?
The last Cutscene takes place before the final level. It will have Luigi talking to Mario wishing him luck, but will NOT be playable on this level.
So what do you think? I added one. Also, the next demo release is planned for March 9, the day of my birthday.