Big news for those excited about the release of Forza Horizon. Developer Playground Games and Turn 10 Studios have confirmed that the game will be getting a full-featured Rally Expansion Pack, which will arrive on December 18th.

The Rally Expansion Pack will deliver a rally experience for Forza Horizon drivers who will get the chance to tackle the off-road areas of Colorado. It promises to deliver all of the excitement of rally driving, with deep ruts, higher jumps and new driving surface types. Of course, the Rally Expansion Pack will include new rally tuned cars, co-driver calls, all new rally events, and (of course) a slew of new Achievements to earn.

When the Rally Expansion Pack arrives on December 18th, it will cost 1,600 Microsoft Points, or if you already have purchased the 4,000 Microsoft Point Forza Horizon Season Pass, it will be included as part of your Season Pass offerings at no additional charge.

Speaking of the Season Pass, it has been confirmed that if you take the plunge and purchase the Forza Horizon Season Pass, you will get five exclusive cars, with one being delivered for download on the 3rd Tuesday of each month starting in November 2012 and running through March 2013. So far, we only know that the first car will be the 2006 Lamborghini Miura Concept as the November Season Pass bonus car.

The number of additional bonus cars is looking pretty good for Forza Horizon, with bonus cars coming for pre-ordering the game, included with the collector’s edition, for playing and downloading the demo, and for buying the season pass. It seems that Playground Games and Turn 10 are making a serious statement with this release, and early reviews as well as the demo are indicating that this is a title worth buying.