My guess, and this is a big long shot based on little fact, but the new deathwatch rpg (insert awesomeness rant/plug) shows the chapter for stormwardens. now, they might be mentioned somewhere in the vanilla codex, but not very much, i cant even think of a special character. this leads me to believe in the near future gw will be putting out a new codex for them and deathwatch was a teaser.
from what is seem, they like stormshields, have tanking abilities (making opponents go after them instead of others), more wounds, and strength. this could make for a really fresh and new codex. i mean, i know next to nothing beyond the info deathwatch gives about them, so im sure it is something people will enjoy discovering.
There is also, the really old black templars and dark angels, who could really use some interesting special characters; and i mean really interesting not just something with a piece of wargear that sounds awesome and does next to nothing...
