Is a sliding genioplasty sufficient? (Photo)

Based on the good xray posted your chin is optimal for sliding genioplaty only, no need for augmentation grafting or vertical reduction.Live photos needed for better advice.

With a corrected bite a sliding genioplasty would be the only lower bony jaw procedure that can be done. But it should be sufficient in your case for a satisfactory chin augmentation result and an improved profile.

I doubt it would be sufficient. You will not have a nice labiomental fold. You need jaw surgery as well 

Thanks for your question and for the photo.
It looks like you have put a significant amount of time (and money) into correcting you bite, and your teeth come together nicely.  Since this is the case, I would not recommend jaw surgery, such as a sagittal split.  This would bring the whole jaw forward and make your lower teeth jut out way ahead of your top teeth.  
A genioplasty is a good solution.  It won't change the bite that you've established, but it give your chin projection.  The benefit of a sliding genioplasty is you can increase projection in the horizontal and vertical direction.  A very big advancement may need a bone graft, but big movement are definitely possible!
Meet with a craniofacial surgeon in person to discuss your options.
Best of luck
Dr Rodman