This is a somewhat old story. I joined a project in making a 2.5d platformer in Unity. A couple months in, the project manager had decided that this game would have two sequels, an MMORPG, a live-action movie and a web series. He informed the whole team of this decision. One week later, every member of the dev team had left. This scope crept forth from the depths of hell and ruined a simple project. Lesson learned: Keep the scope small and don't bite over more than you can chew.

Edit: I know that you should dream big, but don't make 4 games, a web series and a movie simultaneously.