
10GbEthernet and FC8 are completely different technologies, addressing completely different needs in IT infrastructure.
10Gb IP switches are currently very expensive and really only make sense for high speed core IP networking. Driving storage blocks over IP is still a relatively new technology (Fibre-channel has 10+ years of knowledge/experience) and customers looking for reliable high-speed deterministic performance will look to FC8 rather than 10GbE for the foreseeable future.
I do believe that ultimately we may see FC over IP, just as we see iSCSI (encapsulated SCSI commands over TCP/IP) at 1GbE today.