As far as I know, they didn't go to the conclave of light (and I think every other 'goodie' race did), and won't be getting an army book in time, so do you think they'll take part?

I personally think they will be in it, thanks to our new fluff (in the beastman book), but it's scary when we haven't been mentioned in the lead-up.

Thta would be my assumption as well, they are more then likely to take part as GW tends to allow all armies to play in campaigns [look at tau in EoT]