I've been considering upgrading my system from 14.04, but have been reading that LTS releases are probably the best for the long run. That being said I noticed that Ubuntu 14.04 will be discontinued after April 2019.
At this point there do not seem to be any other Ubuntu releases with dates beyond April 2019 so my question is what will be the next LTS release from Ubuntu? Or... which release will be maintained the longest?
The usual Ubuntu documentation spots haven't been updated yet, but it is expected that 16.04 will be an LTS release, and that it will be supported until 2021. As can be seen on the Ubuntu wiki page on LTS:
The graph there was last updated before the current latest LTS version was released.