Update 39's introductory text apparently says something to this effect:
"Update 39 is a quality-of-life update focusing on bug fixes, new Events with rewards, new style Motifs, adjustments to time-consuming Achievements, arrival of new Achievements related to Excavation/Scrying and your Character. New Endeavors also be implemented (Dungeons and Trials)."
A variety of other cosmetics and emotes including another generation of "customized actions" that modify your character's harvesting animations or the color of their teleportation have been confirmed.
It seems likely that the trend of packaging polymorphs with Crown Crate bundles will continue.
Note that all things datamined do not indicate any guarantee of Zenimax Online Studios releasing these products to players in any given timeframe.
Please keep in mind that discussion or posting of these datamines on the Official ESO Forums is prohibited.