Well, I doubt the contract the band has states that they're not allowed to release songs on the net, but I suspect they'll mostly work on new songs to be included on albums. However, it is not uncommon that some songs are left out of an album simply because they do not fit the theme of that album, so we might get to see some of those again.
Or maybe another song spurred on by world events, such as Legion of Stoopid was.
DISCLAIMER: Despite my status as your Moderator-Overlord, I am not privy to any special information on this subject. The above is the most I would expect the band to do (e.g. I don't think they'll make a random song just to post it on the net).