Think its likely flyer rules will be in 6th edition main rules personally and that flyers will be 40ks "WFB monsters" as several models eg nightwing and ork fighta have been mentioned randomly at the past that it is conceivable that these are already done and when 6th edition comes out then they will be released as an accompaniment to 6th edition
Most of the recent army lists have had a flyer at one point or another (stormraven, doomscythe and Razorwing) so I would imagine that they could do it so that every army gets some kind of aircraft /anti-aircraft release (poss rhino hyberios conversion pack maybe) hydra, nightwing, fighta
I Guess if chaos comes out soon if they have some kind of flyer / anti then we will know then