They are still playtest material.Interesting that they still say "This is playtest material".
I don't see why it is unlikely to see these two new classes released in Fall 18...?It's unlikely they'll do two heavily player class-crunch books in subsequent years. So… 2019?
Based on Mearls video, that seems a fair bit off.I'll bet they didn't want to update them yet to get them out asap. Next update will be AL legal and I bet they wanted to give folks a heads up asap.
I don't think that's a concern for WotC.I don't want to design something and then have the official version cone out and replace my design. Like working on a buffing artificer that empowers armour or weapons and have that be in the book.
Or have to throw out all my content and completely redesign. Such as if the final version is a 1/2 caster rather than 1/3.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.