Is Dave Grohl Going To Be On The New MASTODON Album?

We already know Mastodon is currently in the studio working on a new album. Recently, the band posted new photo album on their Facebook page, and there was an interesting photo included of Dave Grohl hanging out in their studio, which wielding a sweet lucite V guitar. Surely, this must mean Dave is guesting on the album? Perhaps a few licks and a few vocal tracks? Then again, he could've just been in town and decided to stop by and hang. I'm sure this question will be answered soon enough. This album needs to come out already! I'm starting to get impatient.