Nanoha 4th Series to Launch as Manga
It's been awhile since the third season of "Magical Girl Lyrical Nanoha" ended in Japan, & aside from the announcement of the first series being adapted into a theatrical movie, there hasn't been word about a new season coming out. But now all that has changed, & a fourth series is in the works. But it wont be an anime series this time around. The official continuation of the Lyrical Nanoha story will actually be told in manga form.
Sure there have been Nanoha spin-off & adaptation manga in the past. For instance, another separate new Lyrical Nanoha manga called "ViVid" will also be launching later this year. But unlike "ViVid," this one is actually being treated as the true fourth "season." It will run in Newtype's new bishoujo spin-off magazine Nyantype, which is set to launch next month to compete against Megami Magazine.
Titled "Mahou Senki Lyrical Nanoha Force" (Magical War Chronicle Lyrical Nanoha Force), the story is set five years after the end of the third season "Nanoha StrikerS." Notice that the title is no longer called Mahou Shoujo/Magical Girl, but rather Mahou Senki. This is because Nanoha can't reasonably be considered a magical girl anymore. At 25 years of age, she's now 16 years older then when the first season originally aired. The lolicons were already angry about how old the characters were in StrikerS. They're probably furious now that their precious Nanoha-chan is now an old woman.
Source: http://www.animenewsnetwork.com/news/2009-03-06/lyrical-nanoha-4th-series-to-launch-as-comic