Firstly, Wilson, i'm going to start with you. Its not the capacity per se thats the issue. We have one of the oldest grounds in the country (probably, haven't checked. Don't feel the need too.) Fact is, its outdated, and for the reason you've suggested.
You can't keep adding shit on top. Its like Buckaroo. We've expanded, updated etc all we can and we're at tipping point. We've got an old tiny little stadium and it just doesn't befit the club. I'm sure we have one of the smallest pitches in the league. If we're to compete, stay at the top and stay relevant, we need to maximise the earning potential of our assets. The stadium is our biggest asset and currently theres fuck all else we can do with WHL than play football. And i know people will say "well i don't care about anything else its our ground i just want football, etc etc" but if having One direction start their world tour in the 60'000 capacity white hart lane 2.0 means more money for the club, thats money that isn't coming out of our pockets. (Well, unless you choose to go to the one direction gig of course.)
Essentially what I'm saying is, Yes, we can knock down the east stand and rebuild. And the north. and the South. And the West. But then, thats actually far more expensive than it is just just build a purpose built state of the art stadium.
Which leads me on to my next point. We're not planning for 10 years here. Or 20. Our current stadium has lasted us over a hundred years. (well, sort of. We've had the same stadium like triggers had the same broom). So For all those in the "yeah but we won't sell out a 60'000 stadium every game so whats the point" camp. The point is, well A: quite obviously, the more seats there are the more we have the potential to earn. But also B: what about in 50 years time when 80 million people live in London alone. (give or take...) and even West Ham are getting crowds of 50'000 to their shitty games let alone the good ones. The population is increasing and that means more people are gonna want to attend. Id happily sit in a stadium with 15'000 seats sitting empty for 10 games a season, for the next 20 years. If it means we can get all this shit out of the way now and be ready. Imagine if things did start to go well! We don't want to be the shitty tin pot club in the champions league that only allows 5000 away fans because our ground is so fucking small.
A bigger ground will mean we can avoid situations like Benfica earlier this year where i was up in block J surrounded by portuguese fans.
Finally, to all the doubters. All those saying this is happening because the stadium is going to get built. The fact its gone to a CPO doesn't mean it might not get built, it means the land is basically 99% ours now, we just have to agree on a fee. I can't see any reason why all involved would want to delay this. The sooner it happens, the cheaper it will be.