Vice News has this report on its lawsuit against the State Department on the FOIA request for Hilary Clinton's emails. State is seeking a delay until January of 2016 to release the emails.
It's unclear from the article why State can't make rolling releases of the material. Further, the timing is probably not good for Clinton's presidential campaign as the release would come about two weeks before the Iowa Caucuses.
Update: It looks like the Judge had the same idea I did (maybe he was reading the FOIA blog this morning!) State has been ordered to make interim releases of the material according to the AP and former Secretary Clinton has also urged State to move faster.