I've always thought a cool firewire device would be a 5 1/4 inch bay mounted break-out box with USB, ethernet, legacy ports (including PS/2) and maybe even SCSI/IDE. It'd be a good way to shrink any future motherboard.
If all that I/O chokes the firewire port just add another independant channel. It'd still take up less space than a single parallel port connector.
Just my 2c worth. :-)