People believe what they want to believe – this will make no difference. While the carbon dating is somewhat ambiguous (and gives more than enough wiggle room for believers), this will similarly give those who don’t believe in Islam, the complete certainty this completely disproves Islam without any further consideration.
I myself do not believe in Sky-Faeries, and many here will rush to blame Religion for most of mankind’s woes (or perhaps more specifically Islam more than most) but the real problem is adherence to any ideological Dogma and cherry picking or distorting facts to fit your Dogma.
Don’t be expect to win any friends or converts by trying to push this down Islam throat as proof Mohammad is not divine. It will be seen as a Zionist/Christian/American plot to deceive the faithful.