Just in case you wanted the info:
The third series' title is "Full Metal Panic! the second raid" and will be done by Kyoto Animation, director Takemoto Yasuhiro (same person as FMP?f)
Author Gatoh Shoji says: "I will be fully involved in this third installment. There will be anime original stories and characters and will do my best not to disappoint fans!"
Source:
http://d.hatena.ne.jp/moonphase/20040807