So, in theory if you're here, you've arrived from our weekly Thrones recap. If not, you may want to go there first. Ground rules again: This is speculation about where Robb and Talisa's storyline is headed, which, judging from their scene in this week's episode, "The Bear and the Maiden Fair," may be a slightly (or more than slightly) different destination from that in the books. But I'm going to describe what happens in the books, so if you haven't read them get out now. This really isn't something you want spoiled. You may also want to bail if you'd rather avoid spoiler-y (though unconfirmed) speculation. And, again, please keep any discussion of the subject in the comments here rather than in those of the main recap.
It had seemed to me for a while that in changing Robb's bride from Jeyne Westerling to Talisa, and in expanding her role substantially, Benioff and Weiss might be steering her toward a different endpoint. Specifically, I thought that, unlike Jeyne, she might attend the Red Wedding and be slaughtered along with the rest. The coming bloodbath hardly needs another body, but this seemed in keeping with the showrunners' efforts to make her a more significant (and more sympathetic) character and to emphasize her loving relationship with Robb.If you're looking for evidence of this possibility (as I am), I think you can find it in her scene with Robb this episode. It's the most romantic scene the two have shared yet, which in Martin-world is a pretty good predictor of impending tragedy. Plus, there's her announced pregnancy, which would make her death just the kind of dialing-up-the-cruelty in which Benioff and Weiss specialize.
That said, there's another more interesting (and mutually exclusive) Talisa theory that's been making the rounds, and you can find evidence for it as well in this week's scene. It's called the "Lannister Honeypot" theory and it holds that Talisa is, and has always been, a Lannister agent, sent by Tywin to catch Robb's eye, entice him to break his engagement with the Freys, report back on his activities, and generally help him to lose the war despite winning all the battles.
The best rundown of the theory I've seen is here: