Can you tire of the green hill zone? If so then you might want to avoid the new Sonic Generation demo altogether. If you do however have a soft spot for the spiky blue wonder and his luscious bumpy surroundings, then grab yourself a demo celebrating Sonic’s 20th birthday on June 23rd. The demo will be released in multiple regions and will be available for a limited time; supposedly July 12.
Thanks to Siliconera for the info.