I'm not aware of any land that didn't eventually sell at auction, but I doubt we would release it to public. Most likely we'd hold it and find another use for it.
Oh, dear, that is peculiar. Please note that auctions have been closing with 0 bids. Here are two examples:
Seefeld (172,100) Mature 16080m Parcel
Warmouth (114,125) PG 10448m Parcel
There were others earlier. Sorry to keep asking, but there seems to be something going on here that Linden Labs is not aware of.