I don't know, but I doubt it. The sorbate will work as a preservative while the flavoring is in the bottle, but probably not as a presevative on an entire batch of beer.
Sorbate doesn't kill yeast- it stops it from reproducing. So, if you've still got yeast in the beer, it doesn't even need to reproduce to continue fermentation.
Keeping it cold should inhibit the yeast far more than any sorbate would.