If it does switch, i doubt it will be immediately. 4e as a baby will have only a sparse population of what 3.5 had in terms of races/classes/monsters and rather than making awkward substitutions and patches to the system to figure out what to do with bards, half-orcs, etc, he's better off just waiting until he can paint with a full pallette. I can see him waiting for as much as a year or two before doing the switch, if only to give people time to learn the rules of the game. 3.5 rules jokes are funny because they're familiar to us and we've probably experienced it, 4e jokes will need time to get the level of familiarity to be even half as funny. How can he make a 'paragon path powers choice' joke when most of the readers have probably not even cracked into thoses much more than once or twice. Will he go 4e? Only if he likes what it does to the story, and only when it would be a benefit and not a sloppy cheap twist.