No instance cluster shipping with Riders of Rohan
Sapience has confirmed that there will be no instance cluster shipping with RoR. He also hinted at a new type of repeatable content, which is presumably meant to keep end game people busy until the instance cluster hits:
We are working on an instance cluster. Currently it is planned to be part of an update due to release after the Riders of Rohan expansion has shipped.
Rohan itself will be released with a new type of repeatable content.
We’re not really talking about either of these things at the moment. Even the press is just getting a very rough overview, but you will be getting more information about both the cluster and the new repeatable content later this summer.
There has been no indication yet as to whether the cluster will be a part of either the pre-purchase expansion bundle or the turbine-point option.