I easily give you that people still have an interest in building Torres copies or Romantic guitars nowadays - forgive my rhetoric use of the word never. My point was about the evolution of the standard size, in relation to the average size of the players.
Standards are not cast in stone and you should expect them to keep changing, looking forward.
Some changes are driven by attempts to improve on the sound (say: lattice bracing to improve volume), some others are driven by attempts to optimize the matching between the player´s body and the instrument (say: the armrest). Some changes will succesfully spread and become standards (the 650 scale), some will be dropped (tornavoz).
For sure, we are all tall compared to a Ukele, yet a Ukulele has to be played with a different technique than the one you use for a classical guitar because the instrument has different dimensions, also in relation to the human body (replace Ukulele by Guitalele if you find this compares better with a guitar).
As to the trend increase in average mankind size, it is quite well documented (for instance here
). However, this is only indeed an average, and differences occur accross people and regions in the world.
I am just betting that overall the average standard guitar size will likely change in response to this average trend increase. But I wouldn´t see this as the most significant change to expect, looking forward. There are so many other things going on.