I don't think this will happen. Most people will probably cope with ads. So Google will keep making business that way. But the ones that don't want to see ads

I don't think this will happen. Most people will probably cope with ads. So Google will keep making business that way. But the ones that don't want to see ads may pay Google instead of using AdBlock. Also, some publishers may decide to use Google's solution instead of an in-house one, which allows Google not to be bypassed. If all that was to fail, I'm sure Google will find new problems to solve and more ways to grow revenue.