I still want to hear the original versions to the songs they re-worked for Danger Days as well as the ones they totally didn't release. They played that song called "Drugs" at that concert as well as the original version of "Party Poison" before they "started over". They said they recorded 28 songs and then started over... It makes me think that they saved a few of the "best" demos from Conventional Weapons to be used for a fifth album, or the break up could have been in the works for a while and they are saving a few songs for a "Greatest Hits" album.
Considering the amount of repeating parts in Conventional Weapons, I'd say those songs are probably it. If they had more songs in the barrel, they could have put CW out as an album and made more money. I don't see MCR being the kind of band that will release disjointed, just-because-we-recorded-them songs after a break up just to make more money. Of course, the label probably has a lot of say in that but MCR have always been on great terms with Reprise so I still don't think it'll happen.