They'll exist, doesn't mean they'll be relevant, or profitable. If I were asked to bet against the stock, I probably would. Everything about their valuation and IPO smells to high heavens.
It's a shame that what started as one of the most private messaging apps around still doesn't use end-to-end encryption and has since been surpassed by many on that front, though.
I would bet that they don't end up completing the terms of the Google contract as signed; and that it would be heavily modified by year 3 of the contract.