The official site just reported that the title update for the Xbox 360 servers has been approved by Microsoft, so most of the content from the past few updates will be hitting the servers this Friday! Unfortunately, Forest of Illusion will not be included with this update. An official reason why has not been given yet.
According to chillaura at the official PSU forum, the content from this update which has not made it to the PC/PS2 servers (PM devices, Nanotranser X, etc.) should be added with this Friday's maintenance. We'll have more information as it surfaces.
Update! Despite SonicTeam not listing Forest of Illusion in their schedule, the mission has indeed hit the 360 servers! Happy hunting, Guardians!