Officially, Showtime announced the limited series’ return as being for one season (Season 3), however, filming insider account @ForLocations recently tweeted (since deleted) that filming has wrapped for two seasons:
“Twin Peaks is wrapping up its first two seasons [..] Yes – first 2 seasons.”
If correct, it would mean Twin Peaks Season 4 has already been filmed.
Source and more: RenewCancelTV
Screenshot: Welcome To Twin Peaks