await isn't an alternative to TPL/Tasks, it's a feature that improves a certain common use case of TPL/Tasks. "await foo" means (roughly[1]) "yield and schedule the current continuation to be run on completion of foo". What really requires language support is the "current continuation" bit, which starts to become tricky/convoluted to express directly once control flow comes in.
For any use case other than this there are other tools, such as WaitAll/WaitAny as you say.
I make it a rule never to question Eric Lippert, and I won't do so here. That said, right, the current continuation bit requires IL foo, but as the ones writing the code, there is always a way besides needing the current continuation bit.
And if you're going between languages much at all, Tasks are a lot more like promises and other paradigms in other languages. Whereas the whole await business is just... weird.
For any use case other than this there are other tools, such as WaitAll/WaitAny as you say.
[1] http://stackoverflow.com/questions/4070237/how-could-the-new...