The phrase "additional upside" means there is more potential for gain or positive outcomes beyond what has already been mentioned or expected. Full definition
If you like the company, the cost control, the diversification with earnings strength abroad, then you see the yield as competitive with bonds and plenty of additional upside. (oldprof.typepad.com)
If they find a way to do this than there is additional upside in the shares. (capitalobserver.com)
Even with the stock returning 40 % in our fiscal year, we believe there is material additional upside. (ensemblefund.com)