FWIW, the current planned dates for these are:
Wheezy LTS EOL: May 2018
OpenVZ RHEL6 kernel EOL: Nov 2019
(sources: https://wiki.debian.org/LTS and https://wiki.openvz.org/Download/kernel/rhel6 )
Perhaps an option is to adopt a similar model to Debian LTS - i.e. support is on a "best-effort"...