As you may know, the Linux Mint developers have previously announced that Linux Mint 17.2 will be code named Rafaela.
Recently, the Linux Mint developers have announced that a RC version of Linux Mint 17.2 will be released in June 2015 and will include important new features, updates and bug-fixes. Among others, a newer kernel will be added, the code base will switched most likely to Ubuntu 14.10 and Cinnamon 2.6 and Mate 1.10 will be available on the Cinnamon and Mate flavors.
Also worth mentioning, Linux Mint’s Clem had announced that Linux Mint 18 will be released sometime in 2016.
As you may know, the Linux Mint developers have decided to use only the LTS versions of Ubuntu as code base, for their new operating systems, by creating only point releases, between two major releases.