Technically I guess you could do this with RSS, eg. site A submits the content of the expired auction to site B, which turns it into a post. This can practically be done already, if you have two different WP
sites. But I think it'd be hard to implement it within a AppThemes Auctions theme, since it'll still be run on a separate server etc etc
Anyway, I am weighing in to say that I'd also love to see an auction theme! But then again, I'd rather see improvements on Classipress!