This, to me, seems a little late to start filming. I hope that it doesn't get delayed. I, however, am not in any way versed on how television is made, so this could be entirely normal.
Well, for Agents Of SHIELD, they film episodes roughly 6 weeks before they air sometimes. Or, at least thats how it was during season 1 and season 2. The episodes in season 3 and season 4 have far more editing, so the development time might be higher now.
However, your fears are comfirmed anyway.