According to Doshin Web (Hokkaido Shimbun) it seems that the Fighters won't be including Terrmel Sledge on their list of players to hold on to. If Sledge is not on that list, he'll automatically become a free agent on December 2nd.
The Fighters have already begun negotiations with Sledge, but according to the article, the two sides seem fairly far apart. It's also possible that the Fighters might be waiting to make any serious offers until after Sledge has tried his hand at free agency.
In either case, the article makes it seem as though Sledge will become a free agent come December 2nd.