Well they haven't made Ras and it took awhile to get Scarecrow, I don't know. As much as I'd like to have a 1/6 Catwoman and Penguin, I could see them just passing on both of them and focusing on TDKR and/or releasing a "V2 Keaton" in the form of the Returns suit to compliment this version.
I mean, would they really make a new, unique true type for the Penguin? A one and done where they can't reuse the body again?
That right there is the main reason I doubt HT will make a Penguin.