I figured Kelly would do the Eldar Codex since he did the last one but I am fairly certain that isn't the only one he is working on now. I mean, we have Tau, Black Templar, Dark Angels, Eldar, SoB, and Chaos (not in any specific order) that all are on the rumored next codices list. Whilst I know there are more authors, it doesn't seem that he wouldn't be doing another one of those. I am not saying that Kelly has to be doing another, just find it unlikely. Cruddace has not done anything lately really which is why I share you assumption that it will most likely be him. I am also kind of hoping rumors are true and Tau is the next codex though, someone did bring up the point that it may be a bad thing if it does come out before 6th edition of which, the point made very good sense.