Belkin will have a DB-9 serial sync cable available in early February.
There is a definite need for this, since many Axim owners need to communicate with electronic equipment that does not have USB interfaces and likely will not for several years. I can not think of any high end electronic devices that incorporate USB.
In the meantime, NT4 users can sync using the IR port of the Axim with a serial to IR adapter.
XTNDAccess IrDA PC Adapter