New details just posted in a new article
on the ESO site:
Throughout Tamriel, you can find new Jewelry Crafting Stations (including set stations) that allow you to create custom jewelry for the current crafted item sets, and you will be able to complete Writs and Master Writs like any other crafting Skill Line. Note that the Summerset Chapter is required to use the new Crafting Stations.
Odd to gate a basic full craft behind optional content although I suppose, it's not any more odd than a new class or BGs as they did with Morrowind or the way WOW gates classes and other things behind their Xpacs.