Once someone supports EME, they would support anything written for EME. I don't believe there will be a way to 'grandfather' any old systems. That would require

Once someone supports EME, they would support anything written for EME. I don't believe there will be a way to 'grandfather' any old systems. That would require either a complete rewrite of the plugin in the browser, or a rewrite in an EME compatible code, in which case it will run anywhere EME exists. secondly, isn't the situation you describe exactly the situation we have now with flash/silverlight? I can't play WMAs on my Mac, Flash on my Droid, or any other number of combinations.