As of September 2002, the versions are:

These models are software upgradable via MIDI sysex messages.

Nova Laptop 4.1
Orig Supernova 4.1
SupernovaII Rack 2.0
SupernovaII Key 2.0
A-Station 1.06
K-Station 1.09

These models are not software upgradable. The OS is stored on an EEPROM chip which must be installed by a service center.

Bass Station keyboard N/A
Bass Station rack 1.5
Super Bass Station 1.9
Drum Station 1.3