No, you can either run them side by side (ngUpgrade) or move to angular 2 incrementally by first upgrading to angularjs 1.6 then going to angular 2. From there

No, you can either run them side by side (ngUpgrade) or move to angular 2 incrementally by first upgrading to angularjs 1.6 then going to angular 2. From there its a matter of moving up the angular 2 upgrade path. The initial rollout of angular 2 vs angularJS was a confusing shit show (and will bite anyone getting into angular brand new as they hit constant google results for one angular when they want the other), but the upgradability is a case study in how to do it right in my opinion. They really made it accessible for anyone to move an app over.