I doubt they will be unsupported. They have a datasheet for Apocalypse, I'm sure they have just decided not to FAQ them and instead wait until the new Codex SW.
Sure i'd let you use them in a game.
Just expect to take the downside (for you) on any rule confusion with your book applied to 5th Ed. As trying to argue for the upper hand with a codex that isn't really supported is a tough thing to do.
Dark Angels 1750 win/loss Record
Win - 23 (Belial helped wreck Ryan's puny Eldar)
Loss - 13 (Brice's Necrons wiped me)
Draw - 2 (The 13th hold out in alpha take and hold)