Personally,(from nearly 60 years of owning/selling) houses,I would hold onto it until you need to sell it.
Most buyers at Auction are after a bargain,and the reserve prices are usually MUCH lower than the market price.
I think the market WILL rise again,just when and how long that will be is another matter.If you hold onto it and sell it in the usual way at least you have some say how much it goes for,given that you can set the asking price and decide how much (if any) reduction you make.You can also refuse offers,which you cannot do at Auction.
If(as you say) you may have 3 years till you have to decide,I would wait and see.The market is in a bad way now,BUT I don't think there is going to be a BIG drop in prices.Even if there were,after 3 years things should start to look up again.