Are there any advancements on the horizon (next 5-10 years maybe) that would enable treating black triangles between teeth by addressing bone/gum instead of filling the space with veneers/crowns/composite? is it conceptually possible down the road?

See a periodontist..: if your dark triangles are up by your gums, then you can see a periodontist about a gingivitis graft to "fill them in". I'm confident you'll get good results if you are a good candidate. I'm guessing you have gingivitis loss due to heredity, poor oral hygiene,, or a bad habit like smoking. Either way..go get a consult from a periodontist and then maybe you'll smile BIG.

Orthodontic evaluate: Depending on why you have dark triangles, you may wish to have an orthodontic consultation to realign the teeth if the problem is not due to bone loss.