Will it be better?

[tdg]

Personally, I think that if you believe that the best that can be made by Frictional is the Penumbra series (or a game there of) - You are setting the ceiling far to low!

The games were great, but I feel lacked a certain level of polish that could have really improved them.

I don't want to nitpick though... so I'll just say that I think the next game should be better if for no other reason than this:
The FG team (small as it may be) must have learned a hell of a lot from building their previous games. The application of that knowledge should lead to something new and interesting. And in all probability, better. :