As you noted duly, there will be a Youtube app for iOS.

You also noted the move might bring ads and other unwanted noise. It will certainly. Someone has to pay for the service.

Now, what will be interested to see is how many people switch to Android because of it. My guess, close to 0.

Of all the videos I watch online from major sources, I have to give it to Google, their ads are the least annoying (possibility to minimize them or quit the video ads after 5 seconds).