Nothing of note just yet. Main thought is they will be a part of a "Free Peoples" book. Which will probably Empre and Bretonnia plus what ever other new stuff they decide to put in with them.
But as for rules, while I havnt played any games with or against them from what ive heard thru the internet/podcasts the rules they got for AoS makes them a pretty brutal army. with rerolls and buffs to attacks on the charge and buffs and abilities that interact with charging. To what is considered on of the best shooting unit in the entire game. But like with anything in AoS its all about the synergies and how you stack those interactions together.