I don't think the collapse of advertising is necessarily a collapse of Google. Google (Alphabet, really) has so much IP and many other possible ways to grow that if crap hits the fan they can change course. Not to mention they do seem to be generating plenty of revenue to keep people interested in buying their stock. So long as Wall Street is willing to bear the weight of their ventures then I don't see Google going…
What percentage of their revenue is from advertising right now? Over 99%, right?
Which is a lot, but it's still $3+ billion in non-advertising revenue quarterly.