First of all, I guarantee a native Youtube donation/subscription/tipping service would already have far more users than Patreon even does currently (see twitch.tv for a great model) due the enormous network effect Youtube already has. Second of all, $1 billion and growing rapidly for a third party service. Nearly every quality Youtube channel I am subscribed to has a patreon at this point, and I can only imagine it increasing as a percentage of income the content creator generates.

> Can you still extrapolate from this that the tipping model is even anywhere near a threat to Google's ad based business model that they should be incorporating it?

No, but we can extrapolate from twitch, and guess that it probably would be.

> Many creators don't use Patreon in spite of or to replace ads, they use it as a supplement.

Because it is a third party site, there is no such option. It would be trivial to incorporate an ad-free experience for donations/subscriptions similar to how twitch does.