There's a nice write up in Vulture on viewership, and how Showtime wasn't just in it for the ratings. While The Return didn't hit the marks of even their least popular shows, their subscription rate went up 11%, and assuming half of those subscribers stayed for the full 3 months, that's actually good news for them and the series. Not to mention future DVD sales, which I have to admit, I'd love to own it all rather then have to stream it. It's also worth noting that Hulu is involved in this, as that's the platform I went to for the "Showtime Add-on" and with it, seasons 1 and 2 of Twin Peaks, along with Fire Walk With Me are all available on the service. Granted, I'll be killing my subscription before it renews, so that'll also play into whether Showtime thinks it's a success or not, but considering they've said "the door's always open for Lynch" it's up to Lynch and Frost now whether they decide to do another season. I could go either way, honestly.

http://www.vulture.com/2017/09/twin-peaks-the-return-was-it-worth-it-for-showtime.html