Years ago I remember an interview with Kerry and Jeff where they said that despite both of them mostly being credited with the songs many were written separately and brought together later. So it could well be something as simple as the three of them haven't sat in the same room and discussed anything specific, but they have been working with stuff and as yet Kerry hasn't be sharing. Kerry reportedly wrote most of God Hates Us All by himself only getting input on his own songs when they entered the studio.
I remember years ago there was a push for the big 4 and then the bay area 4 and then something else and then something else. The silly thing is none of the fans really give a shit, they just want music. When those Big 4 concerts happened a few years ago I guess they were a really good draw card for fans but there was so many stories about the bands fighting with each other very few concerts got reported on without some sort of bullshit over shadowing them. I've got the Big 4 DVD and looking at the show I don't really think I would have wanted to see it live.