Probably February 28th, according to this quote from the Producer's Letter:U66 Drop ?
Well, historically speaking, the typical alternative is the update launching the week after Preview 2 - in this case that means SSG rushing out an update next week despite a number of largely untested new changes and several features on Dragon Lord still not working, so personally I'd say it's worth a bit of a wait.Well with all that ample time, the update will be 100% bug free (rolls eyes) !