Ok, I got a wild hair and decided to put finger to keyboard and type all of this out. Read at your own peril.

My evidence that the next DLC will include the Virmire Survivor:
1. Cameo appearances of Ash and Kaidan in ME2 - Much like Liara, Ash and Kaidan had a very small appearance in Mass Effect 2. Remember, these were the three main characters from ME1. Other character such as Garrus and Tali got a much bigger role in ME2 as squad mates and additional love interests, but they were also susceptible to the suicide mission (read: they could be eliminated from the storyline), these 3 (minus the sacrificial lamb) characters could not.
So what this means to me? The plan has been in place for their bridging downloadable content from the beginning. Liara's is out...the dlc content that featured her put in place the aligning of the Shadow Broker's resources being at Shepard's disposal for ME3. The dlc that will include the VS will resolve the Alliance and Cerberus issues.
2. The Shadow Broker's dossier files sans Ash and Kaidan. Yep, with those two missing from those files allows the writers to be free with the dlc. If there had been a write up for them, that would have pretty much painted the writer or writers in a corner. Remember, as it is now, LotSB can be played pre or post suicide mission. Ash and Kaidan's story hasn't been told yet at this point, so why include something that might break continuity?
3. Adm Hackett's story of defending Shepard even after reports of his/her involvement with Cerberus in ME2. I wouldn't be surprised if Hackett plays a part in the DLC.
4. Adm Hackett's dossier on the SB base - "... A deep cover operative is scheduled to replace his current aide in two months." So, this tells me that the old SB had already set his plan in motion to infiltrate Hackett and the Alliance before T'Soni took over. We have no idea when this dossier was written so it could already be done. This would be a perfect set up for Shepard finding out about any move that is made against Hackett and the Alliance by Cerberus (through the SB's undercover plant). That could be the trigger that ignites the DLC.
5. The Evolution comic - much in the same way that the Redemption comic was the prelude to the LotSB dlc, this comic will prelude the next DLC. The comic also included a brief conversation between Gen. Williams (assumed to be Ashley's father) and Jack, soon to be TiM. Why Williams if not to set up the connection from the comics history, to the dlc? They could have easily mentioned Williams in passing. I am willing to bet that before the comic series is over, they will mention the connection for biotic children and the need for experimentation to "catch up" with the other races biotics.
6. We know that the dlc yet to be released includes "bridging" content yes? Well, what major plot lines have to be bridged? We know that resolving the Shadow Broker story had to be done as the conflict to retrieve Shepard's body was a major storyline in this trilogy. Again, it involved one of the three major, original characters that could not be tampered with during the course of ME1 and ME2 (I say three although one of the three were bound to be eliminated in ME1...the character that would best represent Shepard's personal ties with the Alliance is still in place, regardless of what decision you made on Virmire and the result WAS the protected character through ME2).
Another major plot line has to be the Alliance and Cerberus. Cerberus is a rogue organization of the Alliance. The Alliance has labeled them terrorist. With the recent events of ME2 and Cerberus bringing Shepard back, the Alliance will be even more intent on bringing Cerberus down. Since Shepard has ties to both now, this puts into play a very large moral decision on Shepard's part, and all decision presented to Shepard in ME2 lead to an inevitable conclusion: what side will he/she take?
What other
major storyline needs to be resolved before ME3?
Yes, some of this is conjecture, but I think I present a pretty decent argument for the case of VS DLC.
As always if I am totally off my rocker, feel free to chime in...but be nice, I bruise easily.