I was concerned reading the 50,000 figure yesterday but various things have been said that make me think it will be more like 55,000-60,000. Just my own opinion though and conclusions I have jumped to.
Dave Downey (I think it was him) had been interviewing Joe Anderson and was asked afterwards what size he thought it would/should be and said 60,000. That could have been his own opinion but you'd have thought he'd have discussed that off camera with Anderson and if that was a deluded estimate Downey wouldn't have said 60,000.
The Kings Dock back in 2003 was due to be 55,000 and that was under Kenwright. We know Moshiri is ambitious and wants us to compete with the other 3 Huge NW clubs (said so with his Koeman/Hollywood comments). So why would he settle for 5,000 less seats now when around 03 and 04 we were averaging 38,000 as we have the past 2 seasons. However this season we're set to average over 39,000 with every game sold out, which was never the case back in 03.
Slightly less convincing is my own belief that despite leading people on too much last summer, the Esk does know certain things (called the 5pm announcment and media leading stories from 1pm the day before), and him and various other people have suggested 60,000+. I think 70,000 is far fetched though which I am sure he mentioned.
Of those 3 though, I think the second point is the most reassuring and would make no sense now that Moshiri is involved. Building a 50,000 seater would also not really push us on at all other than the iconic location. It would put us on a similar level to Sunderland and Newcastle and not Man City, Liverpool, Arsenal, Spurs and Chelsea who are clubs we need to be competing with if we are break in to the top 6.