Do you have source for such promise? Isn’t it actually OpenWRT devs’ decision whether they add support for Omnia or not? Besides, TurrisOS is still OpenWRT and all the fancy stuff is either necessary (like the btrfs root file system on the eMMC storage), or completely optional (like foris, autoupdater, etc) so they can be uninstalled. So in my opinion this is OpenWRT-compatible.
I don’t think upstreaming linux kernel would anyhow help in supporting Omnia in upstream OpenWRT/LEDE.
However, I think it’s actually a good idea to have a bare OpenWRT-like Medkit image, which would act more like a normal OpenWRT router, even though it would compromise few security features of TurrisOS, like no default password or DNSSEC validation.