When a framework matures to a certain point usually its a good idea to start again. This might sound counter productive but its a good chance to learn from the mistakes you made the first time and to create something without legacy code that may not be needed.

For awhile this has been the goal for the new .net frameworks with libraries becoming increasingly modular so especially on servers, you only used what you needed.

In an attempt to go a step further, asp.net and .net have forked off and created the core 1.0 frameworks which have been developed from scratch. Both 4.6 versions will still be available and maintained while the core framework matures into something that is production ready.