UA process questions

Can someone explain the general UA process? Specifically, I'm wondering how long it will likely take for the Villainous subclasses to be be playable?

If you like what you see, you can always build it using the homebrew tools and play it today.

But official printing, as wganarokkr said, is a crapshoot on when or if we’ll get it.

And sometimes, UA can come from multiple books, even if they might have a single theme when put into UA, they can be released at different times.

And if the Unearthed Arcana involves blowing up the class/subclass for something entirely different, expect a half-baked version of the original to be released, as they likely didn't give themselves enough time to react when something is roundly hated.