I would like to see a
4 1/4 to 4 1/2 inch closed 3 blade stockman
3 1/2 to 3 5/8 inch closed two blade Barlow, with a Clip or Spear main and a full size Sheepsfoot secondary.
As for the blade steel, I am not picky. Their 425HC seems to work well. I would like to see Buck bring out some with say 1095 or some other carbon steel as an option, without an exorbitant price premium.
EDIT:
I would also like to see them bring out a 4 blade Scout/Camp knife, with a bail.
A Scout maybe 4 7/8 inches or so closed would be cool.