This review may contain spoilers. I can handle the truth.
Ok, so at the end of the movie there is this scene where Charlie says he "wants to get in the family business" which means that someday he wants to become Santa Claus like his dad.
However, the process of becoming Santa, as already established early in the movie when Tim Allen accidentally makes him fall from a roof, needs for the current Santa to die.
So, yeah, Charlie is definitely planning to murder his own father on that last scene.