At the time of this writing, there is no recent version of pgfplots available
for any ubuntu version.

However, there are some user-maintained package repositories where to get
pgfplots. These directories will be updated from time to time; watch out for
updates.

We recommend watching the package archive maintained by Johannes Reinhardt on
https://launchpad.net/~johannes-reinhardt/+archive/ppa
The page also contains instruction how to tell the Ubuntu package tool to
acquire packages from this source.