Personally, I think the X-rays would be a waste of time and money. Even with the X-rays, it still may not exactly determine your future height. There's a lot of other factors: sleep, eating habits, etc.
If you already hit your growth spurt, you may grow two more inches, maybe three. If not, then you still may have a chance to grow.
(6'5 with a shoe size of 14-15)