Finding out if an Ubuntu release is still supported on the command line?

Running ubuntu-support-status will tell you how long support lasts of everything you have installed, here's the output of mine as an example:

Support status summary of 'ivory':

You have 1904 packages (75.7%) supported until April 2021 (5y)
You have 14 packages (0.6%) supported until January 2022 (5y)
You have 83 packages (3.3%) supported until April 2019 (3y)
You have 237 packages (9.4%) supported until January 2017 (9m)

You have 80 packages (3.2%) that can not/no-longer be downloaded
You have 197 packages (7.8%) that are unsupported

Run with --show-unsupported, --show-supported or --show-all to see more details

EDIT 11 July 2021:

In newer versions of Ubuntu (verified on 20.04) ubuntu-support-status has been replaced by ubuntu-security-status

$ ubuntu-security-status
2553 packages installed, of which:
2073 receive package updates with LTS until 4/2025
 467 are receiving security updates with ESM Apps until 4/2030
  10 packages are from third parties
   3 packages are no longer available for download

Packages from third parties are not provided by the official Ubuntu
archive, for example packages from Personal Package Archives in
Launchpad.
For more information on the packages, run 'ubuntu-security-status
--thirdparty'.

Packages that are not available for download may be left over from a
previous release of Ubuntu, may have been installed directly from a
.deb file, or are from a source which has been disabled.
For more information on the packages, run 'ubuntu-security-status
--unavailable'.

Run hwe-support-status to get a simple result. Use --verbose option, otherwise user will see nothing if the system is not using LTS Enablement Stack.

Example result in 14.04 release with existing kernel:

$ hwe-support-status
$ hwe-support-status --verbose
You are not running a system with a Hardware Enablement Stack. \
Your system is supported until April 2019.

The above command is provided by update-manager-core package on Ubuntu, which is the same package that provides ubuntu-support-status command.

$ dpkg --search support-status
update-manager-core: /usr/bin/hwe-support-status
update-manager-core: /usr/bin/ubuntu-support-status

End users will just need this command: hwe-support-status --verbose