Before COO was released, many people theorized that Saint-14 would appear, and he does have his own quest line. But what about Mida in dlc 2? Let's start with what we know about Mida. All of this info comes from the lore for the two Mida guns.
1. There was a group of Mida Colonist on mars, likely on one of its poles (the narator of the Mini tool lore mentions frozen water). Like Earth, Mars has frozen north and south poles.
2. Most of them were either left or were killed off (possibly by the Vex, the Mini Tool detected their teleportation signatures).
3. The Mini Tool is an "A.I. marvel," so it probably has an A.I. or was made by one.
4. The Multi Tool may be from a alternate dimension, making it out of Zavalas's jurisdiction to ban (Shaxx should have let him ban it anyway. It would have saved the Crucible).
Now lets review what we know (or think we know) about dlc 2.
1. It's on one of Mars's poles. We know this from the Arecibo adventures's ending (MARS! RED SAND! ICE CAPS!) and the art for dlc 2.
2. It has something to do with Rasputin or another warmind. Again, Arecibo and the art.
3. There is a woman on the art who could be a number of people (I think it's Ana Bray) but that's not important right now.
Finally, let's see what lines up: The biggest thing is Mars's poles. I don't think it's a coincidence that Bungie made sure to have both Mars and Ice in both the adventure and the gun lore. Secondly is the A.I. The fact that a warmind will be a big part of dlc 2 and there is a Mida A.I. could mean something. While this is mostly speculation, it does still sort of match up. Maybe the Mida A.I. is a piece of Rasputin stolen by a rebel group who wanted to create a new colony on mars, and used it in their weapons.
Until the dlc comes out, we can only speculate, but who knows? Comment any critiques or theories of your own.