I'm not too keen on online multiplayer personally but I do enjoy a good co-op game! I agree with everyone saying that multiplayer shouldn't be shoehorned into a game for the sake of ticking boxes, but trust JAW to do whatever they feel is best. From what we've seen so far, it is obvious they care about the IP and are not just in this for the money, so I'm confident that any decisions would be made with due consideration. If a multiplayer element maintained the game's style and atmosphere, and was fun to play, I'd definitely check it out
Regarding DLC, I was thinking recently about how the game design of AO lends itself well to being able to download extra levels. Many of the secret areas in AO and AE were in many respects self contained areas, often by means of a portal being in other locations (such as jumping through a portal in scrabania and ending up in that green RF level not used elsewhere).
Similar to being able to download extra challenge maps for the Batman games, we could see something like a new RF zulag package, consisting of a series of stand alone puzzles and challenges set in a new zulag (with a different colour or something), maybe time trial leaderboards too and trophies!