Not really. This airport has been proposed many times before, and rejected on each occassion. All that has happened now is that one of our leading architects has come up with a specific layout proposal, although on closer inspection, it looks far too much like a C&P job from HKG.
Wrong, there has only been one enquiry that looked building an airport in the Thames Estuary and that was the Roskill Committee. The more recent proposals have not been subject to any formal government investigation or consideration and have not therefore been rejected, they have just had a few words mumbled about them and then ignored which is not the same thing.