It's going to happen anyway. The new PL chief exec met with the big 6 and then pulled out of the job. They're going to make it very difficult for anyone to come in and not be their puppet. If they get a lions share of the TV money, as they want, we may as well pack up and go home.
There's also no way anyone would pump money into our league if the top 6 left. However, I would be interested to see what happens in 5/6 years after they've left. I honestly don't think people would be that bothered in the UK and viewing figures would drop. CL viewing figures are tiny compared to PL games.