Subaru sold the Baja through 2006, Ford sold the Explorer Sport Trac through 2010, and Honda sold the Ridgeline through 2014. Honda is re-introducing the Ridgeline in 2016 or 2017 and now Ram appears to be entering this market as well. I think it's a small market, but it's large enough for many auto makers to have played in it, and it's large enough that at least two are still going after it. The consistent format is short bed with four true doors -- for families looking for car-like comfort with a limited amount of open-bed utility.
I don't consider the Avalanche part of the same market -- it's essentially a re-bodied body on frame truck whereas some of the others, including this new Ram model, are unibody-based. The Sport Trac was sort of an odd one -- offering a compact body on frame truck with independent rear suspension (in the 2nd generation model).