This isn't breaking the fourth wall at all. Breaking the 4th wall is when a character knows that he is a in a show\comic book, while Kami-sennin just said that Nam's gaze was so poweful that it was straight out a comic book.
But there is this actual fourth wall break in the very end of Piccolo Jr. Arc where Kamisennin says to the reader: "No, this is not the end. There is a little bit more"