UPDATE: For clarification, these Pokemon are avaible in game for their current game setting. This event will allow you to get a free Pokemon without need for a trade, as well as a megastone for coinciding Pokemon.
The article has been adjusted to reflect the clarification.
Recently announced, both Pinsir and Heracross will be available for the next distribution event. Pinsir is currently available on Pokemon X while Heracross is currently available on Pokemon Y. You will be able to obtain these Pokemon between August 13 through September 17 via the internet. Gamestop will also be giving out codes to get mega stones to turn these bug Pokemon into more elite versions of themselves; you can get them starting August 18th while supplies last.
It might be worth noting that this new round begins with Gamescom and lasts until the first day of the Tokyo Game Show.