The Heresy-era Legions? Probably not, but I won't say "no". The modern Chapters? Probably, in time.
Once activity increases it has always been the plan to expand the Adeptus Astartes
forum to include subforums for each Chapter with a Codex. For the minute however there isn't enough activity to justify having another half a dozen+ forums sat unused.
For the Legions, the reason I say "probably not" is because TWS is predominantly 40k-oriented.
That said, if with increased activity we found that was a large number of HH players/modellers then we could consider expanding 30k forum
, in a similar fashion to the above.
In short, our plan is to simply try and follow the needs of the board, rather than being pre-emptive. If we add a load of forums that aren't needed (yet) then it simply makes the place look unused. By making changes when they're required we get the benefits without the downsides.
Thankyou for the suggestion though, always happy to hear what people think might be helpful!