Source:
A survey sent to Xbox Live subscribers.

The official story:
Microsoft has not made any announcements regarding backwards-compatibility and does not comment on rumors or speculation."--Microsoft representative.

What we heard:
As the launch of Microsoft's next-generation console nears, the amount of rumors surrounding it is reaching critical mass. One of the biggest points of speculation is whether or not the device will be backwards-compatible, given current-gen Xbox games are designed to run with a 40GB hard drive and credible photos of the Xbox 360 show it with an optional hard drive.

However, this week, numerous Xbox Live users reported they were sent a survey that explicitly stated they will be able "to play against gamers who are on Live through Xbox 2--as long as they are playing a current-generation Xbox game." Although Microsoft would not officially comment, the volume of the reports and the clarity of the survey's wording make it a near certainty that at least one model of the Xbox 360 will be backwards-compatible.

Bogus or not bogus?:
Not bogus.