Why would they switch? These are new features they haven't been using and which probably aren't available on Silverlight or WebGL. Switch because they're adding an option you don't want to chose?
If a company has no plans to use these premium features, then yes, I would imagine they will continue along as-is with Flash.
But a last thought; a revenue sharing plan like this will make big players nervous - what might Adobe starting charging for next? It will cause developers to start at least considering alternatives.