I'm wondering if the end of Net Neutrality, and the ability of competing ISPs to throttle the competition, makes 4k more difficult and less desirable for Netflix?
And the delivery of HDR a more desirable option?
The title of the Forbes article seems a bit like clickbait to me, and I think a more accurate title might have been "Netflix Says 4K HDR Trumps 4K SDR - And Expects You To Pay More For It". The CNET article Forbes used as source material states: "Known as Ultra, the new tier would allow four devices to receive Ultra HD video and audio streaming simultaneously." It doesn't look at all like they are running away from 4K.
Rather than being an alternative to 4K, the new Ultra plan appears to be an attempt to move two features (HDR and 4 Screens) of their existing premium plan to a entirely new tier. So if you want to watch your favorite shows in 4K on 4 screens in all their HDR glory it looks like it might cost a bit more soon.
https://www.cnet.com/news/netflix-rumored-to-be-introducing-new-ultra-plan/