Re:Angular 5.2 Now Available – Angular Blog
by eitland on Wednesday January 10, 2018 @05:10PM
(#16119620)
FWIW some tools including an official one from Google exist to help in migration.
I've worked with both 1.3-1.5 as well as 2, 4 and 5 and if I inherited a 1.x codebase I'd rewrite it, if necessary one piece at the time.
2+ shouldn't have even used the Angular name IMO.