If you're prepared to wait a couple of months, Ubuntu 16.04 (due out in April and a Long Term Support release) will have 5.6 and 7.0 and you won't need to rely on a PPA.

If you are planning to upgrade but use the PPA in the meantime, make sure you keep a careful watch on the version numbers as I don't think it's particularly easy to switch from a PPA to the main repository for a package if the PPA version is higher.