What potential does my horse have?

Honestly without a video and/or photographs of his jumping ability and style there's no way any of us can tell you what his potential is. His pedigree, height, and age can all be factors but are largely insignificant compared to his actual ability. I've seen horses bred from Grand Prix jumpers who are unable to organize their legs over trot poles, and I've seen back-yard bred pedigreeless horses jump four feet.