Use this command:
ionic lib update
This should automatically detect the latest stable setup for the overall environment and update to it.
Off course it asks and confirms eg like this :
Are you sure you want to replace \stMobile\www\lib\ionic with an updated version of Ionic?
hope this helps 
when i do
`ionic lib update`
it asks me:
Are you sure you want to replace /Users/username/project/www/lib/ionic with an updated version of Ionic?
(yes/no): yes
and then there just is:
Invalid version: undefined
What’s the problem?
Ionic components are migrated from bower to npm. But we would need a migration guide to update to the latest version. I am also facing same problem and waiting for the community to prepare a migration guide from bower to npm.
Same error for me.
Did you guys find a temporary fix ?
Do not update for now or else create a new project and copy your www files (except lib folder) and install plugins again.
Follow the new documentation on ionic.io for configuration of ionic cloud. Also one important thing to note is that ionic analytics is not available in the ionic cloud library till now (because i was getting error and it is not there in documentation too) so refrain from upgrading if you are using it.
Migration guide is there now.