If Flash, Silverlight, and Unity Web Player were based on open standards and they each had as many competing implementations as there are web browsers, then they might be a real way forward. They're each useful in their own way, but their application is limited because they're each locked to a proprietary implementation.
Granted, Silverlight was "open" in the sense that it had defined specs, but the specs were clearly written by a single company, and competing implementations would be at a significant disadvantage.
Adobe/Macromedia tried to take a step into standardisation for Flash ( ES4 ) it failed ,because some were pushing crappy alternatives ( Microsoft and Silverlight ) and Mozilla had cold feet ( tamarin ... ). Funny how some now try to shove you typescript when we could have had a better language back then.
It doesnt mean that we will still be writing some javascript in 10 years ,hopefully we wont.
Granted, Silverlight was "open" in the sense that it had defined specs, but the specs were clearly written by a single company, and competing implementations would be at a significant disadvantage.