Are Click packages obsoleted by Snappy packages?
Should I focus on learning how to make snappy packages, and ignore the click documentation?
Click is still in use for the Ubuntu Phone, but that will migrate to snappy pretty soon.
Snaps in 15.04 are the new click, but even they are still in development.
The target form of snaps will be in 16.04 LTS, where they become compressed filesystems, so totally self-contained and totally, provably, immutable. That's where we finally get the perfect transactionality and also space efficiency we want.
My recommendation would be to start playing with snapcraft now, it's a neat way to make snaps, and it will handle the transition to the new format naturally for you. Anything you build with snapcraft today will become a new-style snap when that's ready.
According to the web page linked below Snappy is just the new name for Click packages
see http://news.softpedia.com/news/ubuntu-desktop-built-with-snappy-packages-486556.shtml
"The Snappy packages, formerly known as Click packages, are a new approach to package management that allows for transactional updates, and they also provide better security."