They are currently talking about branching, so we will have the nice framework we are (somewhat) used to and a whole 'nother way of doing things, which you can see if you have Visual Studio Community and there are some mysterious choices for types of applications called ASP.NET 5, if they have not changed it to Core, its new name. You can get a bowl of popcorn every week and sit down for https://live.asp.net/
where the team tells you what they have been doing, although I would say it is advanced shop-talk. There are also announcements on it somewhere in microsoft.com every once in a while. You may wish to Google or Bing it or whatever.
Worry about it? I can't say. You may find yourself in it for the rest of your life or dodge that there bullet, depending on workload, etc. But I think you can now build an MVC application in the new rascal, but not a web form.