Update 45 of ESO will be released on PC on March 10th and on March 26th on console.

New dungeons:

• Exiles Redoubt
• Lep Seclusa

New armor sets: 11 total, 8 from the new dungeons, 3 as rewards

New Houses:

• Shattered Mirror Isle (Fargrave City) - video
• Castle Skingrad (West Weald) - video

Mount changes including faster movement not including upgrades

Zone Updates (visual):

• Betnikh
• Stros M'Kai
• Bleackrock Isle
• Bal Foyen
• Khenarthi's Roost

New Event:

• Crime Wave - rewards for stealing

I think this hits the highlights, but the linked site has a complete list.

Other sources: Arzyel Builds