It seems to me that Abyssal Maw and Firelands, the two new raid instances, are going to be introduced in patch 4.1. There have not yet been any official statements for the releasing of this content but the files included in the latest PTR patch (4.1) speak for themselves. For as I know these maps have not yet been seen by the public; someone might have accessed them but there is no screenshots or other media yet uploaded.
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These are the ADT files I came across when going through the PTR files. They can be found under wow-update-13682.MPQ/world/maps/ in sub-folders named AbyssalMaw, Firelands1 and FirelandsDailies.
I couldn't get them loaded with my modified client as it kept throwing me a memory error/wasn't loading the ADTs at all. I believe all the necessary files are there; both instances have a great amount of ADTs included (over 70), but it could be that the files are partial or simply missing some stuff inside. So after trying for several hours I've decided to let you try. If you manage to view the zones in-game please provide us with some screenshots.
Have fun, I already did
~Xel