I don’t think a company as big as Google could die without a couple months notice. I think most companies would go to special lengths to get their users to setup alternatives. Gmail accounts would get flooded with “hey since Gmail is going away don’t forget to change your login preferences, we’ll force you to add a new email next time you login”. And there would be a massive number of memes like when gpdr took effect.

It would certainly be a chaotic and annoying time, but I think most vital services wouldn’t be so bad and Microsoft would grab a nice little monopoly on office apps again.