3DS at this point would be a really bad idea.
It's at the end of its lifespan (USUM are confirmed to be the last Pokémon games on the 3DS for example) and being replaced by the Switch essentially due to no proper handheld-only-successor in plans.
Even if we were in 2015 or something, starting development of a new game would just be the same mistake as Dark Dawn all over again... a game that had to be reinvented to adapt to the new hardware, just as said hardware is dying out, preventing extremely convenient re-use of the resources for at least another sequel to complement it a few years later, leaving us with a single entry that clearly feels complete but is forced to stand on its own at the same time.