Yes, I also received the same letter and probably going to get Version 6.4 (Nov. 2005). I live in Canada, and owns a 2003 SE Murano with NAV, which was purchased in March 2004.
Here is a quote from the letter if you haven't received it
"As the owner of a 2003 through 2005 model year Nissan vehicle equipped with a Navigation system you are entitled to one free NAVI DVD upgrade during the standard new vehicle warranty period."
Does anyone know how reliable are the anticipated release dates?
Is this an upgrade to the software or the map data? I have iGuidance and they just upgraded the software to include more road map details of Canada. iGuidance uses maps by Navtech (so does Nissan I think) so I was wondering if that is the same reason for Nissan's upgrade to be exclusive to Canada?