If it's been opened the alcohol will react with the air creating vinegar through the chemical reaction of ethanol + oxygen -> acetic acid The acetic acid will be of approximately the same percent as the alcohol once fully reacted so around 8-13%. While it's not a strong acid many bacteria will be killed by it and if sealed properly it's unlikely to cause you harm for a few years...

That being said, it won't taste of wine anymore but instead a very strong stringent vinegar

Stronger alcoholic drinks, usually those over 15% last far longer due to the higher alcohol content which kills germs in its own right- alcohol is far more lethal to living things than acetic acid