During the Twitch TV Livestream on June 21, Trion / Rift revealed or hinted at the next expansion being the Plane of Water.
Supposedly it will not be ALL underwater, just pertain to water in its various forms.
Upcoming changes will include four new souls (healing for warriors/rogues, tanking mage and support priest), companion pets (not class specific ones) will become more important (WoW Battle Pets but more useful?)
Should be interesting to see what TRION does with RIFT going forward, now that the free-to-play model is live and queues are back!
Source: Rift Scene