According to the::unwired, HTC has released the Windows Mobile 6 upgrade for the HTC P3300 (Artemis). This is the last one that it had promised back in April.
The download is free from the HTC e-Club (membership required) and you must register your P3300 to be able to download the upgrade. One you have registered your device, it will appear in the My Downloads section.
Note: The update will replace the current ROM image and will erase partnership and all user data and programs on your device. Be sure to back everything up before you start.
Source: the::unwired