What would you like to see from Frictional next?

[superluser]

Penumbra was great horror with a modern setting. Amnesia is great horror in a 19th century setting.

Stick with horror, but choose another historical time/place. Honestly, I don't think Frictional is ready yet (emphasis on yet) to create a game in a futuristic setting that would live up to their high standards. I don't know if they're even interested in doing that, though.

Let someone else use the HPL engine to create a non-horror game. I think it's actually a good and powerful engine for that, but Frictional has shown themselves to be very good at horror and until they know that they can succeed at other genres, they should stick to it.