What I find funny is that this is, ironically, Microsoft's old strategy but with a positive twist. Embrace, extend, extinguish. Microsoft has already embraced Javascript - we could argue that they brought their own demise as the dominating platform when they created XMLHttpRequest. Now they're extending it.
Maybe I'm naive but at this point I don't fear Typescript extinguishing Javascript. If they send things to ECMA for standardization, they'll definitely prove a point in this direction.
ECMA Standardization means nothing with Microsoft. They will still continue the Embrace Extend Extinguish path, no matter if there is a standard or not. Just look at OOXML to see where MS does not follow their own 'standard'.
Maybe I'm naive but at this point I don't fear Typescript extinguishing Javascript. If they send things to ECMA for standardization, they'll definitely prove a point in this direction.