No, but Visual Studio Code is off to a very good start, and it runs well on Windows, Mac, and Linux, all free and open source. It's not a "rewrite" per se, but a new product with the same name but targeted at developers on all platforms. They are talking about adding enough serious IDE power over time (and the original VS shows that they know what it takes) that they could become a serious power in the open, cross-platform dev world.
They would not need to port all the Windows-specific functionality that has accreted on Visual Studio over the years to become the "new Visual Studio" for developers on all platforms.
Not necessarily. Getting it to work with Wine is probably easier.
I've spent many hours running Publisher in CrossOver Office and never ran into any problems, so this sort of thing is certainly possible for complex apps.
They would not need to port all the Windows-specific functionality that has accreted on Visual Studio over the years to become the "new Visual Studio" for developers on all platforms.