The Sea Elves and the Shadar-kai, originally published as playtest material in this Unearthed Arcana, were officially released today (May 29, 2018) as part of Mordenkainen's Tome of Foes; the Eladrin elf subrace was included as well. The Avariel and Grugach, as far as I know, were not released.
(The book was officially released today, according to the product entry on the WotC site. However, it was actually released earlier on DNDBeyond, and the limited-edition alternative cover versions were available on May 18 in local game stores.)
Note that almost everything from the UA release was modified, including the attribute they get, the cantrip (no cantrip any more, a resistance instead) and the Blessing of the Raven Queen was also relevantly modified. So, if you want to play the actual official version, don't expect the UA version to be any close to it.