"Please note that Lubuntu 12.04 is not an LTS (5 years support), but a 'standard' release, supported for 18 months. This is simply due the fact there is insufficient 'man-power' to commit to 5 years of support."
There is a possibility of LTS for Lubuntu 14.04: https://lists.ubuntu.com/archives/lubuntu-users/2013-April/003941.html
Next steps are 13.10, and 14.04 which should be a LTS version for
Ubuntu. Last LTS (12.04), I considered that we were not ready for such
commitment. I was also unsure of the work needed to make a good LTS.
With more experience, I have now a better vision of this goal.
So, let's make it simple, I would like Lubuntu 14.04 to be a LTS
But claiming we want a LTS its' not enough. First, we need to make it
stable enough, so we can safely claim it's a LTS, because people who
install a LTS want a stable system. But, I also would like to make it
sexy enough to be proud of it, to make people happy to recommend it. I
would like to make it THE release of Lubuntu, the reference of all
Lubuntu releases. To achieve it, I have several goals in mind, items
that I consider we need to finish for the LTS, and I think we can
finish them ...
Read more about Lubuntu's future here: https://wiki.ubuntu.com/Lubuntu/Testing/14.04