First, unless anyone has better definitions, let's define "back end" and "front end" according to their usage here: Is it common to separate back-end and front-end into two positions on web development projects?.
How common is it to find programmers exclusively assigned to back end or front end roles on a team? What's the scope of their responsibilities?
In theory, the answers from question you quoted already answer your question. In a startup, it's a bad idea to have an ASP.NET developer who works only on the back end. In a large company, it can be suggested to have a dedicated developer for every task according to the skills of every person.
In practice, I never saw an ASP.NET developer working only on a back end, even on websites large enough. Also (but this is just my personal opinion), ASP.NET does a really bad job when it comes to separating work among people: it's difficult to have a dedicated C# developer and a dedicated HTML/CSS programmer; it's difficult to strictly separate a project into a front-end and a back-end.
Of course, things change when it comes to very large websites. Not only because you can't develop the whole website alone in a reasonable amount of time, but also because you'll lack the required skills or the knowledge of the overall project requirements.
Using cshtml for views will require more from a "HTML" developer.
Using Bootstrap (or a similar framework) should reduce the need for highly specialized CSS developers.
But I would say that this increases, not reduces, the need to be able to differentiate between backend and frontend. You need to be able to say "Frontend developers need not apply" (in a polite way, of course).
My guess is that in the future in the ASP.NET world the Frontend role in a team disappears but the Backend role will be even more visible in job descriptions, ads.
That is not that different than EntityFramework is reducing the need for specialist database developers (though not for the need of knowing how to handle database performance and how to design databases, it is now a part of everybody's role).
The focus will be on getting developers who can understand and implement business logic. And that is exactly where the focus should be. It is where value is added for the company.