One of my boxes is an S912 but I do not expect to see an NG build and realistically think that it is not worth the effort.
Kodi 19 coming along gives even more reason not to think about the S912 and other older boxes.
And we owners should remember that the boxes will not suddenly become extinct overnight and will happily chug along for quite a while yet.
So whilst some devs may potentially feel a little pressure to maintain backwards compatibility, I would say spend your valuable time on supporting the current and new tech to come along.
Buy the time that the next iteration of SOC’s comes along in the coming months, even the likes of the S905X2 will start to look long in the tooth but because they are are already at the NG level, will survive for longer and become available for song as many move to the next level of tech.