Any suggestion of an AH is speculation right now. Most people agree that one will be added, but nothing official has even hinted of adding one. the only quote is was long the lines of "they are looking for a way to improve the retainer experiance" and that they were possibly adding a search.
I wonder how a search would work. would it give you the name of the retainer and the ward they are currently in? So you find a sword you want for a good price, then run around like a madman trying to find the retainer before someone else snatches up your sword. Then after you get your sword run back and search for more items.
Or maybe it will just tell you the numer of a certain items that are currently for sale, but not the names of the retainers they are on. So then it becomes a wild goose hunt.
Or maybe they just let you search and buy right from the seach counter.... which is basically an AH. I'm guessing it won't be like this though.
One thing I do really like is the "seeking" option so that you can purchase items while you are not at your computer. I found this to be a pretty **** slick feature to be quite honest.