Exploring War Like Worlds.

There is an interview with the developers of Rohan on mmorpg.com.

The new dungeon is also mentioned in the rohan patch notes for the 19-01-10. The new dungeon is for players at the cap of 99.

Go back in time and help Ohn’s army take over Ronelia Castle from Bezemut and the Imperial Guard! Assist Ohn as he obtains the powers of the “Fountain of Creation” from Bezemut, creates the continent of R.O.H.A.N. and becomes the Main God. Or attempt to thwart Ohn’s Insurgent invasion of Ronelia by defending Ronelia and it’s Imperial Guards.

There does appear to be some content for 75 +

Dozens of new quests obtainable at level 75+ (including several that are repeatable)