According to J Eels at Cri Show IV in Fukuoka, JKS said he will make a cameo appearance (one minute on screen) in a new Hong Sisters drama.
Although JKS apparently did not specifically name the drama, the speculation is that it would be the one currently in production. Right now, the only drama the Hong Sisters (the famous screen writing duo) have in production is Hwayugi, also known as A Korean Odyessey. The drama is a modernized version of the famous Chinese classic novel, Journey into the West, published in the 16th century during the Ming dynasty. Keep in mind, though, that neither Tree J nor JKS has made an official announcement, so don't get carried away yet!
Journey To The West was also released as a movie by Director, Producer and Actor Stephen Chow in 2013. Needless to say, it was a fun movie to watch for those who like outrageous comedy.
It will be interesting to see what the Hong Sisters and Director Park Hong-gyoon as well as the cast do with this famous fantasy. It's doubtful it will be as slapstick at Chow's movie, but the Hong Sisters are masters at writing wonderfully funny romantic comedies. But like all of you, I wonder what cameo role JKS would/will have?