They are currently working on the Immelman. The exit is already done, but theres still room for a guess how the immelman will exactly be done.
It looks like we will NOT gonna have a normal, straight Immelman, but more an 'inclined' immelman. I think this will be done because there's simply not enough room for a normal one, as you can see here
in the first two pictures.
A photoshopped picture of the completed Immelman can be seen here
. Though it's believed that it will be a lot more underground and not nearly above the ground like it's in this picture!
I'm sure we will know what it's gonna look like by the end of next week. Same for the Zero-G-Roll. hopefully ;)