Patch notes ahoy for Final Fantasy XIV: Stormblood version 4.01, which is live today (also includes some changes to the base game). You can read a fairly detailed summary on the official site, complete with handy symbols showing whether the change applies to Stormblood, Heavensward, or the main game.
Additions to Final Fantasy XIV: Stormblood include a new Chronicles of the New Era quest called ‘The Hunt for Omega’ (with a level 70 requirement), and a new raid dungeon called Omega: Deltascape (also level 70). Expect new items and mounts as well.
A few balance tweaks like “the strength of certain open world enemies has been adjusted” and “location and behaviour of certain enemies has been adjusted” are listed too, but are missing any further specifics. Again, for the full change log (or what’s been published, at least) head to the Final Fantasy XIV site.