Developers Turbine are not planning any new dungeons or raids for their venerable Lord of the Rings MMO.
Community manager Rick Heatonin a 'Take the Hobbits to Isengard' (I'm still not totally sure either. It seemed to involve escorting low-level players across dangerous areas of the game, from the village of Bree to Saruman's fortress) event on one of the game's servers.
"No new traditional instances and raids are being planned at this time." Said Heaton. He did comment that one of there might be some tweaking or polishing of older instances, but nothing is planned as yet.
Apparently there are also no plans to merge servers, as a significant bug prevents Turbine from doing so.
Lord of the Rings Online remains a popular title with a large community, and recent expansion Helm's Deep added a variety of new content, including large scale battles. Whether that expansion turns out to be the last added content remains to be seen.