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

New dungeons:

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:

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

Other sources: Arzyel Builds