Takayuki Kishi has not mentioned anything to the media, but there is a chance he could exercise his option. He does enjoy playing for the Seibu Lions, but is also interested in finding out what kind of value he has on the free agent market.
If Kishi decides to exercise his option, a number of teams will most likely be interested, beginning with the Rakuten Eagles. The Eagles could have a slight advantage over other teams (not including Seibu) since they are located close to his home town in Sendai.
The Lions may have already approached Kishi with a multi-year extension.
[UPDATE @ 11:42pm]
Kishi has an international FA option and may have some interest in playing in the Majors.
Source: Sanspo 9/27/2016
[UPDATE 9/28 @ 2:09pm]
The Rakuten Eagles are very interested in Kishi and could offer him a sizable multi-year deal, if he decides to test the free agent market. Their offer could be bigger than his current deal with the Seibu Lions (three years, 1.2 billion yen).
Source: Nikkan Sports 9/28/2016
[UPDATE 9/29 @ 1:30pm]
The Lions may have offered Kishi a two-year deal worth around 500 million yen. They could keep their offer on the table even if he decides to exercise his option (something they usually do not do).
Source: Sports Hochi 9/29/2016
[UPDATE 10/12 @ 6:57am]
It might be down to two options for Kishi: return to Miyagi (Rakuten) or stay in Tokorozawa (Seibu). There are several problems with either option. Kishi has struggled with injuries the last few years and may be concerned about the cold weather in Miyagi. The Lions spent a lot on Ernesto Mejia and might not have quite as much left to spend on Kishi.
Heading overseas is also an option, but there might not be a lot of interest because of his injuries.
Source: ZakZak 10/11/2016