It's a known bug, that's why we call this release the "bald release"

The fix has to be done in the database, and the reason is that certain default traits where not stored in the db for old characters. All new characters are not suffering from it, because they store the traits properly.
We are working on a fix right now... in the meantime enjoy your new cool temporary look.
Temporary workaround: Put a helm on and off. That shows the hair until you log out. Thanks to Janner for this hint.