You can watch it here.
Besides the obvious fact that it will follow the manga storyline, I just noticed from the trailer that the new artsyle resemble the manga more. Although for some reason Roy looks fuglier than usual. More details will be given on December 12 along the release of new FMA chapter. The new anime is estimated to air on April 2009 just like the first anime. If that’s the case then it might be possible for the manga to be already finished so they can animate it completely.
BTW my heart won’t rest until I see a glimpse of animated Ling and Ran Fan.