We’ve got a summary below:

RIFT: Nightmare Tide is the name of the 3.0 expansion.
There will be the usual dungeons, raids, raid rifts, slivers, massive dynamic battles, quests, open-world zones, artifacts, new crafting recipes/etc.
Access to all of the above content is 100% free.
Nightmare Rifts are a new rift that has scaling difficulty and “nearly endless waves of foes to test your skills and determination” [r].
New Account-wide Collectible: Minions. Pets that can gather resources, collect currencies, find items and gain their own levels. They will have actual missions.
Level cap will increase to 65. Each new level provides you with a “Mastery” from a list of options based on your Calling rather than you Soul. “Masteries are designed to expand your choice in builds, add new synergies, and let you further customize your character so you can play how you want to play.” [r]
New Equipment Slots – 3 new equipment slots that can either be purchased with a digital edition of Nightmare Tide, or earned in-game.
Current BiS gear (Level 60 Tier 3 gear) will last you until Level 65 and a bit beyond that. Thus, you can gain an advantage in leveling and maybe even gearing up for Levle 65 Experts by continuing to gear up now.
Aquatic and Amphibious Mounts confirmed. One of them being a Shark-like mount.
RIFT 2.8: Madness Wakes currently under development. It will include the new AH system as well as The Nightmare Coast dungeon (prelude dungeon, just like Exodus of the Storm Queen for 2.0: Storm Legion). There will also be a some prelude quests.

Будут новые слоты? Вангую наручи и серьги) ещё рубашка мб

PvE Gear Changes
There’s lots of changes coming for PvE gear.
Tank Gear will still exist in 3.0. However, TOUGHNESS is being removed. Tanks will simply require HIT instead. Other tank stats such as BLOCK and DEFLECT are still going to remain.
A new Tank Stat: GUARD is being introduced.
GUARD will affect party members and allows players standing within x meters of the tank to benefit from a kind of positive effect.
No information was given on what this ability will actually do.
It’s an aura.
If two tanks have GUARD stats on their gear, the one with the higher stat gets applied.