I have a project developed until 6 months ago, an ASP.NET 4.5 C# web site that uses the HotTowel.Angular template of John Papa (the project was started in Visual Studio 2013, now is updated to Visual Studio 2015).
The project uses Angular 1.5.7.
In the Breeze site i'm not finding infos about Angular 2, and HotTowel seems outdated (i'm not seeing updates after 2013).
What should i do? rewrite from scratch the javascript part?
You can stay with angular 1.* as long as you want and migrate parts of your app step by step. At the moment there is no need to rewrite the whole app to Angular 2. Also you can look at https://github.com/ngParty/ng-metadata for a future upgrade path.
Breeze actively develops a new bridge for Angular 2 at https://github.com/Breeze/breeze.bridge.angular2