Porsche has been a huge part of the Forza Motorsport world, but it went missing from the line-up in Forza 4. Turn 10 was not able to find favorable terms that everyone could agree to before Forza 4's ship date, so it shipped without.
At Microsoft's Spring Showcase event last week, Turn 10's Dan Greenawalt announced that they've since settled the matter, finally coming to favorable terms. This means that in May fans will see a new Porsche expansion pack for Forza Motorsport 4.
The expansion pack will include 30 Porsche vehicles, with 7 of them being completely new to the series. Expect 20 new events that bring 5 hours of playtime; these events are pulled into World Tour mode, and the cars are integrated into the rewards system. There are also 10 new Achievements that come along with this expansion.
After this expansion, and including all the DLC content, there will be a total of 625 vehicles for Forza 4.