Well, first of all you haven't met physically so it would only be emotional trauma that you would be going through. And not trauma in the sense of it will destroy your life forever. It's trauma in the sense that yes, it will suck and you'll be upset about it for a while, but if it's not meant to be, then it just isn't.
I've been through plenty of online relationships to know how that feels and breaking up over the internet isn't any easier than breaking it off with someone you've spent a lot of physical time with. The fact is that you have invested your time, feelings, and emotions into someone/something and it's not going to be easy to just break it off like that.
There are always "what if's" in life. Life is far too short, though, to worry about those and to continue on with something that isn't fulfilling you or making you completely happy. If you feel it's what's best, then it's what's best for you. And you are all that matters to you. This person will move on, you'll move on, and most likely it will be for the better.