Last we heard from Mastodon drummer and vocalist Brann Dailor is that a new album should be coming out in 2020. We know Mastodon has been working on new material since November, and according to bassist and vocalist Troy Sanders in an interview with Kerrang!, they're still working on it.
Sanders tells Kerrang! Mastodon has been "sifting through ideas" and was working on new material while they were on tour in 2019.
“We’re constantly creating. When we’re out on tour, we’re always coming up with lyrics, riffs or half-songs on voice notes and the Pro Tools rig we take out with us. The long touring process for Emperor Of Sand ended in July, and we all took a couple of months off. Then we all started calling each other with the itch. Through November, we’ve been in Atlanta sifting through ideas. We’re always moving forward.”
Mastodon also has a new song with Neurosis frontman Scott Kelly possibly titled "Fallen Torches" that was recorded to originally be out in January. The band couldn't get the song out the door in time, so as it stands right now, it's just sitting around. So maybe we'll hear that beforehand?