Bethesda didn't develop this game, they only published it. The game's developer, Headfirst, did have additional Cthulhu games planned but they went out of business.

If Bethesda is planning to publish any Cthulhu games in the future they haven't announced this. However with
At the Mountains of Madness being made in to a movie hopefully this will inspire some more Cthulhu games

There's http://www.gamesas.com/index.php?/topic/1105646-the-most-important-question/ so I'm going to lock this one - we can continue the discussion over there if anyone wants.