HTC has posted the Windows Mobile 6 upgrade for the P4350. The upgrade is available through its HTC eClub (in the My Downloads section. You will need to register to log into the site but registration is free.
Also expected this month but not yet available are upgrades for the HTC P3300, S620 and X7500 Advantage.
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: Pocket PC Mauritius