My Sony A1E Oled and Denon X7200Wa  avr  just received a Dolby vision (low latency) update on both devices and I would like to know if or can the Roku Ultra's be updated to receive the same update or do we have to wait for a 2019 Roku device?

You'll have to wait a new device, but there's no guarantee that Roku will ever support DV due to the licensing cost.

In the meantime, I've switched over to Apple TV 4k recently due to Roku's lack of DV, and other nagging fit and finish issues with the platform. Pretty happy with that decision.