Apparently the rumor seems to have become truth!
Brotherhood is 63 episodes with 5 seasons.
It seems to have been mentioned at Qs and As in "New York Anime Festival" which is being held...from September 25th to 27th, 2009?

Anyway, congrats FMA and Brothehood!

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Theme song's information in September 26th

Maybe they'll be almost full versions.

The new OP
[link]

The new ED
[link]

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First, thank you for a lot of comments, favs and pageviews!

Well, the cover of "Perfect guide book vol.3" was in the official site!
It'll be out in October 10th in Japan.

[link]

I translated Japanese explanation into English as follows.

The guide book thoroughly expounds these important keywords

"The arrival to truth"
"The bond between body and soul"
"The reversible transmutation circle"
"The identity of 'Father'"
and the rest

And the characters answer these questions!
"What is the reason Ed is growing his hair?"
"Where is Mustung's home or car?"
"Do Homunculi need to meal and sleep?"

Also there are following contents in the guide book.

"Ushigoya diary" drawn by assistants
"Hiromu Arakawa's long interview" which was written the story behind the birth
The new side story of for a few days after failure in human transmutation of Elric brothers

Next, there is the new information which isn't still opened in official site about the newest episode!
It seems the anime's original story of "Pinako in young days" will be inserted in the episode 27, and the title will be "The banquet in interspace", but it's completely my translation, so it isn't always correct.
This information is in the official site of young Pinako's cast, so it's doubtlessness.
In addition, it's absolutely my guess though, this episode may be Hohenheim and his family's story, and Pinako may appear in it...for example, around taking family photo before his departure or the short story of "Bonus' Elric family".
Just maybe the episode that Hohenheim was robbed by the robbers when he was riding in caravan may be included too.

Finally, it's completely random though, there seems to be a rumor Brotherhood isn't 4 seasons but 5 seasons.
Usually Japanese animes are made in quarter units, so it's guessed that Brotherhood is also 4 seasons, one year.
I don't know why that rumor came out, but it may be possible if the manga won't end until April next year.

I'm a member.