1. Unleashing - We've had a preview for this already. It suggests an overhaul of the system for Nightmare dice.
2. New Thallain types - Sevartal (svartalf, perhaps--meaning 'dark elf' or Thallain sidhe, I guess), skinwalkers (although J.K. Rowling got into trouble for her portrayal of this myth recently)
3. Revelry - A new way of getting Glamour which appears to be kith-specific (e.g., satyrs will do something related to, I guess, passion).
4. New Arts - Oneiromancy, Contracts, Dragon's Ire (possibly?), Summer (possibly?).
5. Ways to cure the Undoing - This is an important one, as temporarily Undone characters can seemingly be brought back from the Mists. The Second Edition rules for the Mists have characters fall into a coma for months on end, which often interrupted game flow.