Near the release of Isle of Siptah, they admitted that they are working on new character customization options - but it could have been what we already got with Siptah (a few new types of face and hair).
Unless they referred to something else and they haven’t shown it to us yet.
I also remember they were checking a certain system similar to what we saw in mods.
A little hint: What the Exiled Lands map has for a long time and the Isle of Siptah one is still missing?
Answer: Fast travel system / personal teleportation.
They never said if the game would actually receive this feature and they did not associate it with 3.0 update, but still this is my best guess of what we can expect. Which means that there will be something more - such a function would have to be really extended if it were to be the “biggest update” to the game.
Some Pippi mod elements would be wild! But there is no reason to suppose that they will give us anything from it