The biggest breakthrough in limb lengthening will be when they discover a way to facilitate fast healing of bone fractures. Once there's a way to heal a fracture in a matter of weeks, limb lengthening will be a walk in the park.
For tibia in particular. You can use the externals to lengthen (1-2 months) then use the new drug to consolidate quickly - and you're done. No invasive opening of the knee cap, no drilling into the bone, no reaming the bone canal with metal rods. As a bonus, you can achieve high level esthetics by medialisation, and have perfectly straight and well shaped tibia. Without any risk of permanent knee pain. You can also walk around the whole time you're in frames, and there will be only one surgery, not multiple like with other methods (insert the rod, remove the rod, wreck your knees each time in the process). As a bonus number 2, this would be very cheap provided the drug for fracture healing is affordable.
This will be the real breakthrough in limb lengthening, not the stupid Stryde.
How likely are we to see it in the foreseeable future? It's hard to tell. But multiple laboratories around the world are working on developing such a drug tirelessly. Not because they're racing to alleviate our height disphoria, but because fractures are very common and cause a lot of suffering and cost to society (think elderly falls, car accidents and sports injuries). There's a huge market for such a therapy and I don't see any reason why it couldn't be developed.
