Well before planning to migrate, try to answer why you want to migrate ?
New technologies/ upgrades will keep on coming...and you don't need to be on cutting edge always to solve the problem.
Remember, Migrating from angular 1.x to 5 , may become a nightmare. If you have good experienced team familiar with Angular 2/4/5 then plan wisely. Otherwise, drop the idea till the team gets comfortable with it. Modular approach of angular has few problem / or less better solutions to problems you face while creating production grade applications.
We also tried to migrate our angular 1.5 application to Angular 4 and faced a lot of problems. ( Always, Check if your organization is ready for that big architectural change their SLA's , performance points and other things ).