Looking at the trailer, there's a lot of environments shown that are already confirmed as fighting arenas like the Kotal Kahn statue, Lin Kuei temple, Destroyed City, Elder Gods and the Kove. Now what do you think will be new arenas, look at the trailer / these screencaps http://imgur.com/a/1qPRA? My guess:

* Top of the mountain, where the 4 good ones are faced with Kotal. The screencap is perfect with those Asian buildings and the two dragons in the background. This better be one hahah
* Boat / ship where they keep the prisoners
* Army base
* Streets of Outworld (Kotal's empire?)
* Shaolin temple (where the red smoke appears)
* Tower of fight Mileena and Kotal, Rain kicking Kotal, Maybe starting on tower and getting kicked into the streets?