Judging by the picture the horse looks a little downhill. Also, the neck looks pretty thin/small along with the head. It isn't really an 'ideal' mount for Dressage or Jumping but I would still look at it.
I really depends on the horse itself. If it likes what it's doing, if it's willing to work, etc.
For example, Jesse with his dinner plate feet, giant head, and short legs has been trained up to 2nd Level Dressage and can jump over 4ft. He absolutely loves to jump, and is a completely different horse when doing so.
"You know, for as long as I can remember, I've had memories." ~Colin Mochrie