12 August 2010,
Spoilers from EW.com below;

Q: Any chance you could give us the title of Chuck‘s third episode? And if you’re feeling extra generous, an extra scoop on top of that? —Conor
A: “Chuck vs. the Cubic Z,” is the title of episode 3. And since I am feeling extra generous, the title of episode 4 is “Chuck vs. the Coup d’état.”

Q: Who will inherit the role of rotating Buy More spy “Greta” in Chuck‘s fourth episode? —Joel
A: Funny you should ask. “We don’t have a Greta in episode 4,” says exec producer Chris Fedak. Adds fellow EP Josh Schwartz: “The Buy More is not in that episode. Chuck’s away on a mission.”