Listen to the Rock Paper Shotgun podcast on Left 4 Dead 2. There is a fine line between "lying" about the extra content and changing plans for legitimate reasons.
Valve makes a good case for how their DLC plans evolved into a full-on sequel, which is why I think it's perfectly fair if they instead transform their free DLC plans into a discount-for-the-sequel plan.
The whole situation seems very similar to the "canceled Black Box" situation of a couple years ago, where the concession was copies of Half-Life 2 and Episode 1 that you could give to a friend, as well as deep discounts for preorders.