Cover of artbook
Also, if you pre-order through Animate.JP site, you can get a special slip-cover with the drawing done by Arakawa-sensei just for that and that goes over the case for this book.
<Warning! Series Final Spoiler>
Pics of front and back of box cover you get if you pre-order through Animate
ETA: March 24, 2011
More details on the book, thanks to hilary!
For translations on details, go to Tombow's post here.
ETA: Jan. 30, 2011, adding new info, (Product info from animate online shop, as reported by Kirara's post below ^^)
It will come out on April 22, 2011, and it will be 1,699 Japanese yen (plus shipping)
Full-color, 146 pages, A4 size
With over 100 pieces of Arakawa's original illustration artworks for the series, including works done exclusively for this illustration collection, and pieces never been included in tankoubon/magazine publishings before, plus some comments by Arakawa, including some tidbits of stories from the FMA production that were never told to the public before...
Found this scan on Baidu, which has a one-line advertisement about the artbook 3!!
On the Right side page of the posted scan, at the bottom, it simply says:
Hiromu Arakawa Illustration Collection: Fullmetal Alchemist 3 ...Coming in March 2011!!
No other info on this illustration collection book yet.
(For info and discussion on the upcoming new FMA guidebook, "FMA Chronicle", please go to "FMA Chronicle" thread. )