There is no precise ETA for the update, which doubtless means it's not coming anytime soon, which in turn means you'll have plenty of time to "finish" the game in your current world. And then you can just start a new world once the update does arrive, without losing all that much.

That's what I'll do, anyway.

(Mistlands is, in a way, less empty now than it was prior to the update yesterday. My outpost area had been affected despite being a previously discovered area, too, and now looks rather cool. But also creepy.)