Looks like people are reporting that you'll need to have the whole bundle in order to receive the items. This is usually how it goes, the requirement being that you merely have to own the game while a sale's going on for it. Naturally this doesn't happen too often as preorders are the most common offers. You should get your items soon, perhaps even before you read this answer.
In some cases, such as Left 4 Dead 2, buying the game will be enough to reward the items at any time. Most often it's "before the sale, and until the sale ends". You can see the wording here suggests this; for example: "These promotional items were awarded with Genuine quality to players who owned or purchased Mount&Blade With Fire & Sword between April 28, 2011 and May 3, 2011."