I agree that i hope it's in the same spirit of the original series and manga. I'm not really sure about the length, but I hope that they will go into the Enishi saga, as it was such a huge part of the manga, and completely left out by the series, only to be changed horribly by the second OVA.
The problem with the series the first time around was that it was created as the manga was going on, so they had to create all of that filler, and eventually got to the point where people stopped watching and the show was cancelled before it could be finished. Luckily, they wouldn't have that problem this time around.
(By the way, I actually liked some of the filler. The Christian saga was my favorite part of the series. So sad and beautiful.