In reply to johncoxmysteriously:
I said "supposedly". I'm the first one to think that no single route is a passe-partout of any given grade. In an ideal world, each grade should have some 3-5 "classic" routes of extremely different styles. Tick all of them in the same way (OS/flash/RP) and you can say you can really climb that grade in that way.
I wouldn't consider Megos and Ondra youngsters anymore. Sharma was the best performing sport climber at 20-21 too, so I guess we can all agree being 20 is a perfectly mature age for a climber.
If you were referring to the top climbers currently between age 12 and 15, I honestly doubt they'll end up being to Ondra/Megos what these two were to their previous generation.
Adam and Alex are already close to the limit of how much climbing and training you can cram into a growing child and they definitely rolled a 6 when it comes to factors such as advantageous body frame, parents into climbing, proximity to rock climbing spots etc.
Talking numbers, although I believe Adam has already "lost" the crown of youngest ever to RP 8c+ to Ashima (and might be the same for 9a), his OS record from age 10 to 14 is still in a league of its own compared to that of climbers currently between 10 and 14.
The recent preforming kids achieved their hard sends in typical kid friendly crags (Margalef, RRG) and in RP (i.e. might mean loads of beta or guiding from others, specifically set-up quickdraws to help height issues when clipping, you name it). But I really value Ondra's OS as a child as they happened consistently in different crags all over Europe, and with OS you are on your own by definition.
So no, I think you are right, I don't think we'll see anybody flashing/OSing Hubble ever, and definitely not anyone who can be rightfully called a youngster in the climbing world...