Microchip doesn't recommend PK2 anymore just like the aged ICD2, no new device will be added officially under MPLAB, nobody under Microchip will work on PK2 unless there is a serious bug on parts previously supported. (One of the most important PK2 designer left Microchip around April-2009) It may get more and more open-source community events and supports on PK2 own PC software. Especially many PK3 users are mad of the poor design and performance after one year of PK3 release.