Auction Houses now list and allow you to bid on items from both Guardians and Defiants.
Yes and no.
Yes because it limits traffic, no because prices will drop, since there are more sellers. Especially on PvP shards. That means that if no one of your faction was able to farm, some from the other might be able to.
I am not sure of which turn it will takes. But that means that I will have to adapt. I have a AH char on each side of many shards, I will have now to change them for more mules, going from one shard to the other.
No big deal but undeniably more difficult.