Was suppose to happen today. However, they had to push it by seven days, due to a last minute bug they found, which could have deleted some players progress. However, it is still coming, and they are offering everyone 7 day free vip as an apology. Rome update will have an UI overhaul as well. They did release a teaser/trailer of the rome patch.
Edit:
They revaled more:
https://steamcommunity.com/app/534500/discussions/0/133256758578632714/
To me, it's looking very promising. I do hope, however, that the formations that the Roman troops themselves posess won't be OP compared same tier units with a lower level adjutant, as I think getting a an adjutant with good formations is probably going to cost more time and money compared to unlocking a troops own formation.