What will this board be like? Two or three members writing a dozen posts per year?
I imagine it would be a lightly trafficked board. I don't think I've noticed anyone other than sproingie and myself talking about Scala although there may be others who are interested in/dabbling with it but haven't posted because this didn't seem like the place to. But just think of it....you could corner the market on scala game forums. This could be your path to wealth and fame.
I really wonder whether Scala is suited for game development. Java barely is, and Scala seems to be (moving towards) the opposite of what is actually needed for actually developing, maintaining, releasing commercial games.
Game programming certainly isn't on their radar but I think some of the things added to 2.10 like implicit classes, value objects, and macros may move things back in the right direction. I could see a Java core w/ Scala used to define the game logic. For me the question is for those use Scala as a Java++ (Java + traits + closures), will Java 8 (with maybe Lombock or Xtend) mean there's no need to use Scala anymore.
I'll believe it when I see it. For this Scala board to be created, I need a Scala game on Steam

I searched Steam so I could give you a cheeky reply of games that had scala in the name.....but there were none.
A sub-board might make sense for scala questions but I don't think the size of the community is well suited for that.
My original thought was that because traffic would be light, the one sub-board would be for everything scala related (projects, questions, articles, etc).