Hey, fair enough Simon, these are only my opinions/perspectives, and doesn't make them right or wrong ... but it's kinda what I was getting at, not everybody is from the UK or Ireland, things are different all over the world, and some of those people are coming to visit for the RWC.
I guess my points are/were:
1/ The RWC is a global event, with fans coming from all over the world (not just the UK & Ireland), so they might be a different kind of fan/crowd than what you normally get.
2/ They will bring with them their own allegiances and rivalry.
3/ Segregation and/or artificial rivalry isn't needed, because it already exists.
It's only my opinion, but, I believe that segregation exists in football because of violence, not because of rivalry ... I admit that rivalry is a component, but I suspect that for some fans, the violence is more important than the game itself.
In conclusion, you definitely can have rivalry in sport without segregation and/or violence ... it's just a different kind of rivalry ... not all sports have to, or need to be the same.