[UPDATE] Massively has been informed by Turbine that the name RoR is NOT confirmed for the expansion and is contacting Gamerzines to get this fixed. Bummer. We're going to go cry in our corner now.
Turbine's Adam Mersky has confirmed to Gamerzines the plan for a Riders of Rohan expansion for Lord of the Rings online.
Apparently, Siege of Mirkwood will conclude Volume II: Mines of Moria, with Volume III ready at the gate.
"Volume III will kick off with our first content update of 2010. With our expansion this year we've changed the model; you can still expect to receive regular (free) content updates, but they may not map directly to the launch of a new Epic Story. The story will progress and proceed."
He went on to confirm the RoR expansion which will be separate from Volume III (unnamed as of yet) and is slated for release sometime in 2010.
This should make the Riders of Rohan kinship on the Nimrodel server extremely happy.