@kirby4life, the short answer is Gym Leaders should be using ORAS.
To flesh out the reasoning a little; the idea is for Gym Leaders to be as available as possible for Challengers (not the other way around), and that ORAS-first and XY-optional is the best way to achieve this without overly burdening every Gym Leader. This wouldn't be possible with just XY.
This discussion occurred earlier in the year when PPL South was being organized, and even prior to the release of ORAS, and the South GLs came to a similar conclusion. I'm open to discussion
but I think that it'll have been nearly a full year plus as XY is 98% compatible with ORAS, it's not unreasonable.