I am quite excited with this news. If it is true, it will be interesting on how FFG will introduce the investigators based on the factions from Call of Cthulhu. Maybe it the investigators and their cards can be categarized as follow.
Agency - provide fire power to deal deal damage to monsters and cultists as well as being able to put down more allies and gain reinforcement (they may function like cards from Leadership sphere in LotR LCG)
Miskatonic University - for card draw, and progress acceleration (progress tokens will be represented as clue tokens in AH: The Card Game) - (they will be like Lore cards)
The Lodge (The Order of the Silver Twilight) - have investigators that can competent deal with Arcane threats, also provide support against sanity attack, and probably give healing
Syndicate - a lot of "trickery" to delay the threat of the Ancient Ones and to divert monster attack; perhaps may include certain things like board and card manipulation (perhaps incapacitating monsters and cultists, switching places of allies and monsters, etcc), event cards that help investigators to escape from some tight spot and cards that can help delay monster attack and advancement of the doom threat.
Ancient Ones card can consist of location where Investigators has to explore but putting down clues, monsters, and events. Each card can act as as Shadow card like in LotR but the shadow effect will be refer to as Omen effect.
Each scenario will be going against an Ancient Ones and his minions like Cthulhu with his Deep Ones, Shub Niggurath with Dark Young, Mi-Go aliens, Yog-Sothoth with his Sorcerers, Hastur with his artists and lunatics, etc. There will also be specific locations associated with each of the Ancient Ones where investigators have to explore and brave the encounters. E.g. Harbour area (such as Innsmouth associated with Cthulhu, jungles associated with Shub Niggurath, theaters and places with artists associated with Hastur, etc.
Each investigators and allies will be designed to have both Stamina and Sanity value to withstand the attack of the Ancient one monsters and events. Then they will also be given Strength value to deliver physical damage and Arcane value to deliver magical damage or paid for certain Spell cards.
The threat will be represented by a Doom Dial (similar to LotR's Threat Dial)
I'm seriously curious on how FFG will make Arkham Horror into a co-operative card game as it will offer a novel experience in the Lovecraftian context.