User blog comment:FridgeRaider88/Mass Effect 3 Squad Speculation (spoilers)/@comment-743796-20100904121331

There are three characters from the previous two games that are absolutely guaranteed to survive the events of the previous two games: Liara, Joker, and Kaidan/Ashley (depending on who you save on Virmire). So, not to jump too quickly to conclusions, but if Bioware will use previous squad members fr ME3, these are the three that will most likely make the cut. Reasons why:

Liara: I assume after the events of LotSB, she'll be finally free of the Shadow Broker, and thus able to rejoin the squad.

Joker: You do get to play as him in a short segment when the Normandy crew is away from the ship. ME2 showed that the two years between the first and second games provided enough time for technological enhancements to at least partially treat Joker's condition, so if another few years pass, Joker joining the squad is a likely scenario.

Kaidan/Ashley: Yes they aren't happy with Shepard being part of Cerberus after the events of the first game, but at least they had other objectives during the game, and thus not directly involved with the plot of ME2 (save for the mission when they are). Either of them will likely rejoin the squad.

Lastly, I'm sure Bioware will have a mechanism in place, where certain sqaud members can be replaced by others if they died during the suicide mission, much like they did with Wrex (if he was killed in ME1 he's replaced by Wreav). In that respect, Feron (this is only speculation) could be a squad member, assuming he's saved from his fate in LotSB.