It is true that JKII will have dedicated servers, but I remember Quake 2 coming to the Zone during JK's day. I never played Q2 over the zone, but I'm assuming it used the peer to peer mode (which sucked compared to dedicated servers). Since JKII is using a similar engine and LucasArts had the deal with Microsoft to put their games on the zone (I'm not sure if that expired or not), then JKII could very well end up on the Zone. Of course, this would be in addition and secondary to dedicated servers. You'd want to play on a dedicated server anyway.
Swoosh