UPDATE: The Xbox 360 version of Forza Horizon 2 is being developed by Sumo Digital, Microsoft has confirmed, and will be based on the original Forza Horizon engine.
The Xbox One version, meanwhile, is being handled by original creators Playground Games and is built around the Forza Motorsport 5 engine.
Sumo Digital has previously developed multiple SEGA titles, including Sonic All-Stars Racing Transformed, Virtua Tennis 2009 and OutRun Online Arcade, and has been responsible for multiple handheld ports, including the PSP versions of F1 2011 and Split/Second: Velocity.
ORIGINAL REPORT: The Xbox 360 version of Forza Horizon 2 is not being developed by Playground Games, according to IGN's Ryan McCaffrey, who states that the last-gen version is being made by "another studio".
"I've woken up to worries over Forza Horizon 2 also being on 360," McCaffrey tweeted earlier today. "FWIW another studio is doing 360; Playground is bldg XB1 ver off FM5 engine".
McCaffrey's tweet suggests that Playground has been left to focus purely on the Xbox One version, although it isn't yet clear who may be behind the Xbox 360 SKU or how the two may differ.
VideoGamer.com has contacted Microsoft to ask.
Forza Horizon 2 was announced earlier today for release on Xbox One and Xbox 360 this autumn. The game is to be set in Southern Europe and feature a new weather system, hundreds of cars and Forza Motorsport 5's Drivatar system.
More information is expected to be revealed tomorrow.