I just spoke to a kind and seemingly informed person at Mazda USA cust service and was informed of the following:

Mazda entered into an agreement with Navteq to have Mazda dealers (only) provide updates to the Navigation systems as a regular part. This was supposed to begin with the release of the 2007 update which was scheduled for fall of 2008. That release has been delayed and will not be available until some time in January 2009.

So starting in January 2009 you can buy the 2007 update disc from you local Mazda dealer. They should have part numbers and will likely have to special order it.

So if you are like me and still driving around with the 2005 disc you can at least get a 2007 disc sometme in 2009.

No word on how much more the disc will cost when I have to buy it from my Mazda dealer instead of from Navteq.

Cuzzin