let's assume for a moment that the hawks are right, google's core business is threatened and it's on the path of decline without major changes.

Do you think Larry or Sergey comes back? Or too far gone?

design @splits | /wireframe /latenightcrew /event-pass /feud

Not too far gone. Their brand name and foothold are strong. There needs to be a drastic cultural change internally which starts with new management. 

They need to start running lean and make quicker pivots rather than staying glutinous and risk averse.