The notice affect 3.1. There will not be a 3.2 or later 3.x.
4.x is the path going forward. 4.x requires you transition to that platform with its new licensing scheme if you wish to have support for features and platforms not in 3.x or earlier.
The software maintenance releases mentioned in the notice will be interim updates (builds) on the 3.1 base. Those will be released through March 1 2016.
TAC Support (configuration questions, troubleshooting etc.) for 3.x will be available through March 2018.