Just because the latest UA had subclasses and no full class, does not mean they aren't working on one. A full class is much harder than just a few subclasses. You have to design the FULL class as well as 2-3 subclasses to go with it.
I think some of you are reading too much into the most recent UA which only said no Mystic and gave a few subclass ideas.
How do you build a new class with no new subsystems?
Crawford said it repeatedly. People like the themes, people like the thematics, but they don't want new mechanics. The Mindflayer has done perfectly fine being psionic with no psionic mechanics.
Taken together, with people just wanting a psionic theme, but no mechanics wanted or necessary, then that leaves me confused on how you could get a new class.