We have heard from BoK that Tastytaste believes that a Dark Angel codex is next. A couple other rumor mongers believe that while not next, it is coming this year. This gives us a decent idea that there may well indeed be a codex, but will be in it?
Couple things from a week or so ago, we heard about a plasma main gun and plasma sponsons on predators. Alongside that there was an expanded use of Chaplins. There is also the possibility of the Land Raider Ares making the codex, and today's rumor hints at yet another possible unique option for this army. Jetbikers.
Please take a ton of salt with this. Even Bramgaunt when he heard it considered it to be simply wish listing. I am posting this more towards speculation of units that could make the codex, rather than anything solid.
Jetbikers would be an elite bike unit, but the fluffbunny's would go berzerk. I have heard about a jetbike kit, but I labled it wishlisting. They would sell like hot cherry pie, they would look awesome, they could even call them Ravensomething so they wouldn't have to break their current naming policy, it would add to the uniqueness of the army, but I don't see it happening.
If we had such, and this is pure speculation, we would have strong Chaplins and Interogator Chaplins, Plasma gun turrets with side sponsons, a Land Raider Ares, and Ravenwing Jetbikes. Just the sounds of a codex like this is exciting. Once again, its Sunday morning, and this is all speculation, and nothing solid.