As we already said, 1.6 will be standalone version of TESTW and a last big step before 2.0. This version is, in fact, once planned patch 1.5.1 which had grown twice and contains lots of redesign, bug fixes, new architecture for Valenwood and Orsinium, some UI overhaul, few new units, rebalance, script fixes etc.
We unofficially call this version as "The End of the Third Era", because it mostly completes Third Era campaign in a way it should be in 1.5. Of course, in 2.0 we will overhaul Third Era campaign with new scripts and mercenary armies, but most of them will be added in both Third and Fourth Era campaigns. We hope you will enjoy this new version, which, as you can see, will arrive very soon.
See you on 1st December, 2018 in The Elder Scrolls: Total War 1.6