As detailed on amazon, a Porsche expansion is coming to Forza Motorsport 6. The expansion is listed for release on March 1, 2016 and includes:

• an additional 250 Gamerscore
• Porsche exclusive Mods and badges
• All-new career mode – Porsche Anthology campaign featuring 48 events
• 20 Porsche cars
• Porsche multiplayer leagues and new events
• Brand new track, Virginia International Raceway