Hellboy director Guillermo del Toro posted an update on the sequel on DelToroFilms.com yesterday:
Mike and I wrote the screen story together and I wrote the script. But it is NOT based on anything yet published but Mike felt it had a lot of elements he has been keen to explore in the future of HB.
HBII: THE GOLDEN ARMY is currently being “put together” financially by Larry Gordon et al-
HBII is still my number one priority and no one is contemplating my “stepping down” just yet. It is highly unlikely -albeit possible- that it would happen but that would require a series of unfortunate finacial, logistic, personal events that seem remote at best. More likely than not, if the project were to stall I would still be attached as writer/director.
The timing for HBII seems right, what with the anime, game, comic book series, toys, etc. I believe that HB and the BPRD are -more than ever- in the publicÂ´s mind. One bit of good news or all Abe fans. Abe has a really dramatic role in this new story…
Source: Guillermo del Toro