The speculation is the Kim Jong-un will send a high ranking political official along with sports officials to the Winter Olympics:
A North Korean delegation to the Pyeongchang Winter Olympics could be led by Kim Yo-jong or by Choe Ryong-hae, the second-most powerful person in the North.
During his personally delivered New Year’s address, North Korean leader Kim Jong-un expressed his hope that the Pyeongchang Winter Olympics would be a success and declared his willingness to take the necessary measures, such as sending a delegation to South Korea. The delegation that Kim mentioned would presumably include International Olympic Committee member Jang Ung, National Sports Guidance Committee chairman (NSGC) Choe Hwi and Minister of Sports Kim Il-guk. [Hankyoreh]
You can read more at the link, but if he sends his sister to South Korea I think that is a sign that Kim Jong-un is really pushing his charm offensive on South Korea to get concessions after an extended period of provocations. Having his sister attend the games would give North Korea a softer touch internationally with all the cameras on her instead of the sternly faced old men that usually attend these events.