[logicalmind]

I think the problem is that everyone freaked out with the angular 1.x to 2.0 changes. The angular team, not wanting to lose the 1.x momentum, decided to attempt to write a 1.x to 2.0 conversion tool. The major hurdle to doing this successfully is reliably interpreting javascript code such that it can be understand and converted by an automated programming. Now imagine if instead, all that code was written in typescript. Such a conversion tool would be arguably more simple.

It would seem that if you want angular to evolve in possibly non-backward-compatible ways, then conversion tools would be a requirement. And this is going to be a simpler task with a typed language.