It doesn't seem five minutes since Forza 4 came out at the end of last year. Actually, it came out in October. Don't get too comfortable with it though because Forza Motorsport 5 has already been announced. If you think that means you have the best part of 18 months to relax before shelling out on more Forza, I'm afraid you're wrong: the above teaser trailer shows off Forza Horizon, which will be released at the end of this year.
While there aren't really any details on the two games – outside of confirmation of their existence and confirmation that they're two different games – the only other thing that we really know is that Horizon is being developed by Playground, a studio comprised of an experienced team of racing devs.
So it looks like Microsoft's response to its lack of exclusive IP is to try and boost its biggest sellers to a yearly release schedule. Could it work? If they continue to sell as much as the average 360 exclusive usually does, they could be on to a winner.