Depends on how you do it. Of course if you want to move instantly then that's gonna be hard. But slowly moving isn't that bad, or creating new projects somewhere else and slowly porting old ones.
Even then, it's possible that just companies that planned to buy GHE will simply not buy it and use something open source instead.
Even then, it's possible that just companies that planned to buy GHE will simply not buy it and use something open source instead.