It would take far less than that. 90% of their business is selling search ads. The other "HUGE" markets they're in aren't profitable and will dry up as soon as the ads division stops making money. Slowly competitors are pecking away at that business. Google needs another cash cow or a competitor will step up and dominate them.
Just ask Yahoo...
I think comparing to Yahoo is a bit of a stretch now. I understand Yahoo was once on top, but would you agree that it's not to the point where Google is now?
The amount of influence Google has over the web is massive.
List of Google products - Wikipedia, the free encyclopedia
List of mergers and acquisitions by Google - Wikipedia, the free encyclopedia
I'm not saying they can never fall, but to happen in under a year is where it gets to be unbelievable.
Their current power play in the mobile/cellphone market, staring to turn the tides on being an internet provider, the massive amount of marketable data they have on everyone, etc. They're not just sitting on their money and collecting checks.
Edit: Kind of realized I got away from the point of them just not being on top of search, which I still think is a stretch in under a year with the dominance they have in the area. Even if someone had better search technology Google could buy them, and or the new search company would still have issues getting on any of the devices. All these other companies now have their own devices or make deals to become the default search engine on the browser.