We added approx 7000 seats (48k-55k) with the last redevelopment which included the south extention and the seats at the front we know 1500 have come out from the front, so assuming the ss3 holds 5500 and is mirrored in ns3 we would hit 59k, if we wanted a 60k stadium we wouldnt have taken 1500 seats out.Whos says it makes it impossible. From my memory the plan for over 60000 pre dates those extra seats going in, and only some of the extra seats ( that everyone complained about anyway) were removed for the advertising.
So taking the seats out don't make any difference to the original plan for 60,000 plus.
Some of the planning apps talk about 6250 seats in the 3rd tier if this is correct we would probably just about hit 60k seats when including segregation.