Correct me if I am wrong but the only extension to T3 which I think is going ahead at the moment is the addition of three remote stands, nothing more.
Further is this in fact an extension considering the loss of two stands on T3 56 and 57 and the three south Bay stands and 12 and 14 in T1. I think 12 and 14 or one or both of them may be reinstated in due course but the position isn't clear to me.
The larger extension to T3 has not so I understand it yet been finalised or given the go ahead.
Viscount