An Instagram account called TheMTGFinanceGuy started a rumor that a Secret Lair with ten Bob Ross illustrated lands would drop Cyber-Monday, November 30.
After today's Arena update to release Kaladesh Remastered, Reddit-user TsunMar shared a screenshot with the ten lands available through the collection manager.
Manaecho.com found Evolving Wilds with the art from the Bob Ross show The Joy of Painting Season 9 Episode 12, titled Mountain by the Sea .
Evolving Wilds have the flavor text "We don't make mistakes, just happy little accidents," a famous quote from Ross.
Furthermore, Secret Lair: A box of Rocks, with Arcane Signet, Chromatic Lantern, Commander's Sphere, Darksteel Ingot, and Gilded Lotus, plus Party Hard, Shred Harder, with Anguished Unmaking, Assassin's Trophy, Decimate, Dreadbore, and Thraximundar.
With today's Bob Ross lands shown in Arena, the rumors seem to be true.
Update: The lands are still to be found on Arena, but only Evolving Wilds is craftable.