This isn't true and hasn't been true for a while. Angular's ahead-of-time compiler converts the template strings into TypeScript which are then type checked, all at compile time.
Templates frequently need loops and conditionals. In the case of .tsx this logic is in TyprScipt so you can debug it just like any other TypeScript. In the case of Angular such logic is written in an undebuggable custom syntax.
ng-forward contributor here: that is not the ng2-to-ng1 engine. ng-forward is an Angular team sanctioned library for eventually enabling Angular 2 syntax in Angular 1. It shares a lot of goals with what is outlined in today's announcement but is more catered for teams that want to start an app today with the quickest possible migration strategy.
Because Angular 1.x has a long term support plan in place that should see maintenance provided to the framework for at least a couple of years after Angular 2 drops. Another major component of that plan is building out a compatibility layer between Angular 1 and Angular 2.
It's a bit confusing, but basically right now there are two Angular products: AngularJS 1.x and AngularDart. These two efforts are supported by completely separate teams. Now the JS and Dart teams are merging and the new Angular 2.0 will be written in TypeScript and transcompiled down to ES6, ES5, and Dart. So while it may look like jumping around, the message seems to be consolidation.