As promised, Blizzard will be pushing out the next content patch soon after 4.1 has been released. We are already seeing preview videos on youtube and it does seem promising. Some have pointed out that it looks like Molten Core v2.0 but since I never played in Vanilla, I have no issues with it. Definitely, at least, looks fantastic, watching the scenery, the terrain, lava flows and mobs inside Firelands. The textures are just amazing.
There are currently two previews that I suggest you have a look at; one for the daily quest hub environment, which will probably be very much like Tol Barad, and the second preview is on the Firelands instance itself. I am looking at the video, again, and cannot help but be excited when watching the encounters. The spider hanging from fiery webs, the night elf fire lord that transforms into a scorpion and giant flaming cat… almost wish it was coming out tomorrow.