ESM is available for 12.04, which enables Advantage customers to keep receiving kernel updates and updates for many user space packages. In our case it's very important to know if we'll be able tot use Ubuntu 14.04 safely after April '19, because it is not possible to upgrade our application and migrate it to say, 16.04.
Yes, ESM will be available for Ubuntu 14.04 LTS (trusty).
As you can see on the chart which is shown below, Ubuntu 12.04 LTS has already been an end of life release since April, 2017, but its security maintenance has been extended for an additional 3 years until April, 2020, and the security maintenance of Ubuntu 14.04 has been extended for an additional 3 years until April, 2022. You can either pay for ESM on its own or sign up for Ubuntu Advantage which includes it.
The next Extended Security Maintenance (ESM) release after 14.04 will be Ubuntu 16.04.
At OpenStack Summit held on November, 2018 Canonical and Ubuntu founder Mark Shuttleworth said in a keynote that Ubuntu 18.04 Extended Security Maintenance support lifespan would extend Ubuntu 18.04 support from 5 years to 10 years.
Ubuntu Core, with an image size of 260MB, is the smallest Ubuntu release to date. This makes it ideal both for IoT devices and cloud containers. A new release of Ubuntu Core is released every 2 years on even numbered years (2016, 2018, etc.). Ubuntu Core 18 is based on Ubuntu 18.04, and is supported for 10 years.