Shortly before Ace Atkins's Spenser continuation novel, Lullaby, was released, I asked Mel Farman of the Parker estate if there were plans to continue Parker's Western series starring Marshal Virgil Cole and his friend Everett Hitch. Mel said yes, and they were exploring continuing Sunny Randall as well.
I saw a post on the Robert B. Parker Facebook page from last Thursday that news of the Cole and Hitch continuation novel, Ironhorse, was coming soon. I went on to find Ironhorse's information page at Penguin Putnam. Written by Robert Knott, who co-wrote and produced the Ed Harris movie adaptation of Parker's Appaloosa, Iron Horse will be published January 8, 2013.