"While Square will be a much smaller business from a revenue standpoint after the Starbucks deal lapses, it will be a faster-growing one with a much better shot at profitability."
So what is their target valuation when they go public? If they were going for $1 - $2B valuation? I think the world might buy that, but since their last round was at $6B, their investors would probably be pushing for $10B (because if you recall the Box IPO you remember that none of the late stage investors want to take a down round into the public markets) and that is like "Square 10 years from now" valuations.
So lets watch this one closely and see if they can get commitments for all their shares on the road show. And if not, we'll probably see a giant recapitalization or maybe a firesale to PayPal or something.