Half-Life 3 mentioned in Gamescom product listing, but why we probably won't see it
An official Gamescom document listing the many games that may appear at the European gaming trade show has caused quite the commotion due to mentioning Valve's long-awaited Half-Life 3 game.
The key word is "may", and even the Gamescom document's header says, "Information subject to change", which basically means there's no guarantee or even proof that Half-Life 3 will make a showing.
For the record, to help temper your excitement and bring you back down to reality, the document also mentions 2K Games and Irrational Games' BioShock Infinite as making an appearance, although Irrational has already stated that they have no plans of showing off the game following the recent delay. So I wouldn't count on this document being 100% correct.
As for Half-Life 3, Valve has not yet commented on the inclusion of the Gamescom product listing, but did tell LambdaGeneration, "We will have the Steam team [at Gamescom] to meet with developers and publishers. No game showing planned."
While the time is ripe for Valve to make some sort of Half-Life 3 announcement, especially given the fan demand for it, I highly doubt we'll see anything from them at Gamescom. This is likely the case of Half-Life 3 fans getting amped up over a brief mentioning of something they've been incredibly frustrated about for years. I'm sure we'll see a petition about this similar to the one that happened earlier this year.
Sorry to burst your bubbles everybody, but I doubt we'll see or hear anything about Half-Life 3, aside from these rumors, at Gamescom.