Some fans would leave, some would stay. The bigger issue is the loss of ad revenue for the networks though.
If you cut off a game in the 6th inning networks would probably lose over a million dollars in ad revenue. I'm basing that on 6 minutes of commercials (not including pitching changes) X 3 innings = 18 minutes worth of advertising at approximately $50,000 per TV commercial.
Thats a lot of money, even for Sportsnet (which is really Rogers)