The information available on the IMDB website shows that the Bollywood actor Shah Rukh Khan has not signed for any film made on Tipu Sultan.
A video posted by zain khan on YouTube on 20 September 2018 shows Shah Rukh as the Mysore ruler Tipu Sultan in a movie trailer. A disclaimer at the beginning of the trailer rules out any speculation about Khan playing Tipu Sultan on screen as it claims to be a fanmade video which was meant for the purpose of entertainment only. This video was made from several clippings available on youtube.
A twitter user named Kiran Jain (Patriot) posted an image of Shahrukh as a Tippu Sultan but the image was created by a fan and does not represent a commonly released film poster as it has no credits and cast mentioned.