Just to give a general update and what I think is going to happen here.

So BA's A350 has just been moved to station 40 of the production process which means the tail fin and the wings are now being installed. First picture of the tail fin is out. (All over twitter)

Now once station 40 is done the aircraft will be moved to station 30 to get the new seats installed. Now at this point I believe BA will announce the seat because it is essentially no longer behind closed doors as it's now being installed.

(Would've posted a picture myself but I'm not yet allowed to post URLs)