Earlier quoted context omitted.
It will be something that turns out to be a carcinogen/endocrine disruptor 20 years from now.
I know you're being sardonic... but it will likely be another fluorine based chemistry that is hopefully more biocompatible (flush out of body easily), and not cause undue harm. The perfluro- line of chemicals are quite amazing.. if it werent for them being completely obnoxious and stay in the body like lead.
Edit: Ah adding chlorine destroys the ozon layer, what's why.