Usually. There's no policy set in stone, but they generally add bonuses in the second week to get another round of news stories and eyes on the bundle.
There are a lot of excellent THQ games they could add as a bonus: Supreme Commander, Dawn of War II, Stalker, Space Marine, Homefront, Frontlines, Titan Quest, not to mention older Red Faction games or Saints Row 2.
Bravo for them, I say. Looks like the bundle will easily surpass $1 million in the first few hours.