Right now, Liverpool would fill 60,000. Of that, I have no doubt. But for how much longer..?
They'll need to get a wriggle on, regarding getting back into competition for the big prizes or they may as well forget about expansion. For any club in any sport, when your support gets to the size of Liverpool's, there's going to be a large percentage of glory hunters, hangers-on, "experience the thrill of just being there" twats etc etc. It's fair to say, that they don't tend to associate with perpetual 6th to say, 10th placing teams (which is what Liverpool are in danger of having already become).
Then again, i can't blame them for trying. Any way you look at it, they have to expand because if they don't, they won't get any more in match day revenue. Having voted for FFP with all the joy of a dour Presbyterian, they've painted themselves into a corner on that score. It was an act of incredible stupidity and actually one that flew in the face of Liverpool's history when you consider that even Shankley, in his autobiography, credits the foundations of Liverpool with the Pools money (cf references to Eric Sawyer, chapter 7).
So build it and fill it and be successful on the proceeds, is their only viable plan, now. If it is viable (probably, just about, with luck, I'd say). Whether they manage to do it before they definitively fall in with the also-rans, is the thing.
Already, the media have stopped refering to them as part of the Big Four (or even five). That's an indicator of how fickle it's all become. Only a blink of an eye ago, they were ensconced in that bracket. If I had to guess, I'd say that Liverpool have five years (at the outside!) to build a team that will not only consistently challenge, but actually win a major trophy.
Personally, I don't care what happens to them, as long as we're alright, Jack. It's not like they gave a fork about us, not so long ago.