Some parts of the Garmin site now reflects the availability of the new v5. But as usual, it's a mess. For example, you can select to download it from one updates page, but then end up with the 4.20.20 instead. Other links actually leads to the new version.
This seems to be a slightly updated version, with no major new breakthroughs. Maybe that's the reason why your old license is still valid.
Changes made from version 4.xx.xx to 5.00.00:
* Update the look and feel of the Garmin Mobile XT application.
* Add new Garmin Online feature - Google Local Search.
* Add new Garmin Online feature - Panoramio Photos.
* Add new Garmin Online feature - Flight Status.
* Add Speed Limit display to the View Map.
* Add ability to install and display custom vehicle icons.
* Modify 'Peerpoints' feature name to 'Location Message'.
Thanks to beHappy from a Danish forum for providing the news.
http://www8.garmin.com/software/GarminMobileXTforSymbianS603rdEdition_50000.exe