It doesn't matter if esports orgs pull out of OWL; traditional esports leagues like Splyce are pennies on the dollar to Blizzard. Blizzard already has the PR and money under their belt to get organisations like the New England Patriots on board with the OWL. Actual sports orgs like Miami Dolphins probably billions of dollars in reserve that they'd be willing to spend a few million for a spot in the Overwatch League, considering how much Blizzard is promising with this league. The only reason why companies are willing to invest anyways is because Blizzard has been so vague and silent on the League and their buy-in fee is so high that orgs are willing to test the waters to see if there's any actual value to OWL. And if it will, nobody knows.
But there is one thing I can guarantee; The first season will be a success. Blizzard will have several multi-million dollar organizations investing in the League and many big names and a huge amount of advertising. Viewership will probably be extremely high and I wouldn't doubt that some TV network like ESPN will purchase the boardcasting rights to OWL.
The only question is how long Blizzard can keep playing this game until said orgs lose interest or just pull out entirely.