This blog quote:
we've got another update in the works that should be done before the Sniper, and that one will include some new content for all classes.
And the fact that it was mentioned earlier that they were going to implement another way of gaining unlockables without getting achievements pretty much makes it seem like you'll be able to pick up dropped weapons, but you get every single one you walk over, so you have to delete some.
Also: HATS!