The 'Spartacus: Blood and Sand' panel at Comic Con 2009 takes place on Friday
lunchtime, July 24:

http://www.comic-con.org/cci/cci_search_results.php

Unfortunately, none of the reports I have seen list John as a panel member. I'm
surprised, as his character, Batiatus, is a major role.

I'd been looking forward to seeing John at Comic Con again as, last year, when
he was there with 'M3', the convention attracted lots of media attention and
good online coverage with videos and photographs.