No I don't think its too late at all but it wouldnt be an easy road. Seeing as you already have a solid understanding of jumping and find you enjoy it im assuming you're good at it? :) if you have the money to spend on expert tuition you're instructor could see you to championship. You need to find an instructor that has strong competitive jumping background. You're local riding school just wont cut it :) and of course you are going to need a horse that is capable of jumping at that level. You would be looking at thousands of dollars for a horse like that.
You also have to think about your physical health/strength? To compete at that level at that age you will have to be in fine physical health :) not saying that you arent because I don't know but its something to think about.
I say if you can, why not