I'm pretty sure Dell will put out an Axim upgrade and my guess is that they will do what Compaq did & charge a fee for 'postage'. I will call my Dell account manager in a few weeks time to see what she can find out from the Axim product group. ( that's what I did when I wanted to ensure they were shipping the pxa255 before I purchased)
If they do just wait until a few dozen others have tried the upgrade. If it's anything like the iPaq one the first cut will not work.