You got it wrong.
They will be releasing paying, most likely stand-alone expansions every 6-9 months. Every expansion will have atleast a full year of being in the works.After they finished Prophecies, they went to work on Factions, with a smaller team being left to work on Sorrow's Furnace. Then, after the release of SF, they got some new crew, and they now have two full teams working on GW games in shifts.
Sorrow's Furnace was a "here's some thanks for playing!" add-on, not an expansion pack.
TCB Read articles before you call people out as being WRONG!!!!!!!!!!!!!!!!!

(just had to write that)