Google (GOOGL) is taking its time coming up with an ad-free subscription version of YouTube, but it could be worth the wait. A UBS survey found 27% of adults would likely pay for such an offering, higher than interest in online video-subscription services like Sling TV, HBO Now, PlayStation Vue and a potential Apple (AAPL) offering. Among existing YouTube users, 38% were somewhat likely to subscribe and 17% were very likely to sign up and pay. If 5% of US YouTube users signed up, that would boost annual revenue by $943M, net of forgone ad revenue, estimates UBS. If 17% signed up, that would add $2.8B annually