Re: .NET Core is not yet ready for prime time
I suspect that Dotnet Core will never replace the full (legacy?) Dotnet. It may get used in some cloud deployments that were written from scratch to use it, but most of the existing business applications will either have existing dependencies (often through third party code) that require the full version, or the application developers won't be willing to foreclose the option in future versions of using stuff that requires the full version, and so will say the Dotnet Core is "not supported", even if it does work.
I think the main thing that Microsoft is looking for is to have a cut down Dotnet running on Ubuntu, Centos, etc., that they can use as a low priced option for specific workloads on MS Azure to compete with Amazon on price.
I'm not sure how well this will work. Mono was a huge flop on Linux servers, with there being little to no interest in C# or Mono amongst Linux/BSD developers, aside from some demo projects (now largely abandoned). I can't see why this would be any different for Dotnet Core.
On Linux, there is a Java community who do everything in Java and there is a "native" Linux community who do everything in Python, Ruby, NodeJS, Go, C++, Rust, etc. The Java community use Linux, but they largely sit in their own isolated Java world. They will still go on using Java until the Sun expands to engulf the earth. The "native" Linux community by and large have zero interest in either Java or C#. They are not going to start using either.
So for who will want to use Dotnet Core, that basically leaves traditional Microsoft developers who want to start dipping their toes into the open source world, or who are looking to shave some of the cost off off cloud hosting costs. In other words, it can be looked at as giving Microsoft a lower tier offering for price sensitive markets that they can use to try to persuade developers to stay with them by offering development tools that are at least someone familiar to them.