Short version: The Core boxed set had to be redone and rebranded for the Matt Smith era.
The other supplements were delayed until the core box got redone.
The One Ring took up more time than expected.
C7 have brought on more staff to help out (including yr. humble correspondent), so things are moving along again.
Currently, the core box is nearly regenerated. The Time Traveller's Companion is in layout. UNIT got a rewrite and is in editing. The GM's guide is being written, and several supplements to follow that are in development. We're nearly back on track. Ish. Fingers crossed. All going well etc.
Gar Hanrahan, here
And isn't that a great title for the query?