The best thing they can probably do is setup some sort of subscription membership where users pay monthly for it, they'd have to think of some good benefits for what the users will receive though as a lot of people wouldn't pay for this. Definately wouldn't be able to raise this amount of money from advertisements.
If they are losing so much, why do they keep the partnership program up with the highest cpm payments on the web?
The real question is, Are Google competent business people in the first place. It looks like they had their luck with the simple engine script of theirs in 1999 till now. From the looks of it, they are on a spending spree of billions of USD. If they were to lose their one and only source of market share, they would be the laughing stock of the world for being incompetent, and who would hire any business managers from Google to work for their companies? Its true, they have a killer Search Engine, but what if they lose that market? How competent are Google's people?
There has been changes being made to YouTube to help improve revenue. For example, I don't think they had in video ads before Google bought it.