If it went to a pay-to-watch for all channels, No. Even if it was cheap like $5 a month, I mainly put on a let's play or something as background noise while I game or something. And I wouldn't pay for background noise, unless I'm going to actually listen to it (Like music, or a movie or something).
If only certain channels did it. Yeah, I would still view it, since I doubt any of the people I watch (mainly LPs and random uploaders) would charge anything.
If uploaders could choose certain videos for the pay-to-watch, I probably would just avoid those videos, unless it was something I REALLY wanted to see. And even than I could probably find it free elsewhere.