Don 2 has been getting great audience reviews and Farhan Akhat too has spoken on how he may make a Don 3. Shah Rukh however revealed the filmmaker was not keen on making a sequel to Don 2.
"We were not sure. Farhan was like how many Dons will I continue making! But we were not keen on making Don 2 too! It happened as we loved Don. Likewise, Don 3 may happen you never know. We have kept a scene in Don 2 where there's a slight hint that is given about the sequel. Everyone seems to be liking the action in Don 2, so does Farhan" said Shah Rukh Khan.
Source: http://timesofindia.indiatimes.com/entertainment/bollywood/news-interviews/Farhan-wasnt-keen-on-Don-3-SRK/articleshow/11256146.cms
