Recently I had to update my “old” Ionic 2 apps and came up with this little upgrade guide and also an additional script that will automatically do most of the work for you!
The upgrade process is for the most part always the same so this script can save you some time if you have been following the general Ionic naming standards. Of course make sure to backup your code (e.g. with source control) before running the script, I’m not a bash superhero so sometimes it deletes a bit too much here and there (;
You can find the tutorial and script here!