It's worth looking at who's at the helm. You don't make John Riccitiello[1] your CEO just to be bought by Microsoft, unless the price tag is extremely high (possible). He's there to build a huge business, plausibly bound for IPO.
Actually, Bioware/Pandemic made John Riccitiello its CEO just to be acquired by EA (but not before Riccitiello has resigned and joined the EA as the CEO again).
Well, of course, this might have something to do with him being a partner in Elevation, which bought Bioware/Pandemic and, likely, invested in Unity as well (he had been sitting on the Unity board before becoming the CEO after being fired from EA).
UnityScript is so far from TypeScript that would never happen. UnityScript is absolutely nothing like real JavaScript and has none of JavaScript's real features.
The C# is entirely standard. It's compiled to normal IL bytecode. You can call any other IL code from it in DLLs as well, compiled in F# or VB.NET etc. You can even use a newer C# version than their supplied compiler supports if you set it up so you build the IL yourself since it uses the same IL. You lose a few conveniences like opening scripts directly from the editor but it works well otherwise if you want the new C# features. I believe it's also a bit more efficient that way to some degree.
[1] https://en.wikipedia.org/wiki/John_Riccitiello