Contrary to previous speculations and reports, Professor_Wonder said that it is going to be the shape-shifting Jack-Jack who is going to stop Dash from his wicked ways.
As Disney or Director Brad Bird has yet to confirm any plotline for “The Incredibles 2,” it is best to take all information with regards the movie with a pinch of salt.
Just like the first film, Director Brad Bird said that “The Incredibles 2” shall have less on the superhero part and more on the family drama and dynamics.
This line of reasoning actually gives the theory of Professor_Wonder a good leg to stand on since having one of the members of the Parr family as the main villain would make the plotline rich in family drama.
Regardless whether it is going to be either Jack-Jack or Dash who is going to be the villain in “The Incredibles 2,” what seems consistent in the rumors is that it is a Parr family member who shall be the antagonist.
As a Disney movie, the villain would only be good for some duration in the film because it is likely that a realization will come shortly and the family will be whole again before possibly battling a bigger nemesis together.