Eh? This already happened, and Clu won. Every canon source confirms this.
Thing with Clu is that you really can't beat him on the Grid unless you're Flynn, as he is essentially a program duplicate OF Flynn(albeit with perhaps slightly less 'access level'.)
While Clu may not have the privileges required to create programs within the Grid(something only Flynn can do), he does have the ability to rewrite essentially any program(s) he wants -- even those created by Flynn's hand to try and stop him. Hence Flynn's line from the film: "Clu fed on my resistance. The more I fought, the more powerful he became. It was impressive, really."
IOW, Clu's ability to repurpose programs to suit his own needs > Flynn's ability to create them. That's why not even Flynn could beat Clu while inside the Grid -- his only option was reintegration, which seemingly killed them both.
In 'forum-speak' it would look something like this:
Flynn=Admin, Clu=Co-Admin, Tron=Global Mod, and guys like General Tesler=Forum Mods.