I was actually wondering why this was even a co-headline tour at first, because I thought that In Flames should definitely headline. Then I figured out Killswitch Engage actually sold more than 100,000 copies of "Alive or just breathing", where In Flames' most selling record so far(Reroute to Remain) sold like 65,000 units. Considering the numbers that older In Flames albums sold it only makes sense for them to co-headline a tour in 2004, because things are always changing. In Flames is no match for what they were in the late 90s and Killswitch Engage is becoming a strong force(they are the best-selling metalcore act, no matter what you think about KsE or Metalcore as a whole that is a cold hard fact).
As for who goes when, it will be probably like first "As I lay dying" with a 30-45 minute set, then KsE and IF rotating the headlining slot both playing for the same amount of time something like 90 minutes.