The good news is that, in one aspect, current Pilots can be upgraded to the Professional level with a new 1Mb RAM card; the bad news is that this upgrade obviously can't include the backlit display available with the more advanced model.
The launch seems to spell the end of the 128Kb Pilot model. The Personal version starts with a 512Kb memory capacity, and the Professional has 1Mb of RAM. Both machines will include a new financial application, Pilot Money, and enhancements to the PalmOS operating system. There will also be an improved case, but the overall size is expected to remain the same.
Another expected feature is "network compatibility", but no details were given by the source. It looks like the big advantage of shelling out the extra money for the Professional version will be the 1Mb of RAM and an E-mail package.