Die Hard 6 is titled "Die Hardest," which release date is tentatively set for 2015.

As per Screen Rant report, the leading actor of "Die Hard" franchise, Bruce Willis wants to retire his role as John McClane on the sixth installment. "The Sixth Sense" actor, Bruce Willis said:

"In the next few years, they could easily find a replacement for me or call the character someone else. But for me, I want to do Die Hard 5, then one final Die Hard movie - Die Hard 6 - before finally hanging that white vest up for good. At the moment, I can run and I can fight on screen. But there will come a time when I no longer want to do that. That's when I'll step away from the Die Hard films."

"Die Hard 6" title is "Die Hardest". As of the moment, the release date is tentatively set for 2015. The plot summary that Movie Web provided reads,

" The sixth and final installment of the popular series finds John McClane heading out on one last mission to save the world from certain doom."

The franchise movie started in 1988. The first installment is a self-titled. According to Wikipedia, the movie series is based on the 1979 best-selling novel "Nothing Lasts Forever", written by Roderick Thorp. As of the moment, the film series has 5 installements and all series' stories revolve around John McClane (played by Bruce Willis). He is a New York City and Los Angeles police detective. Overal, the movie series has run for 26 years.

The latest installment of "Die Hard" is titled "A Good Day to Die Hard". It was released January 31, 2013, at Leicester Square, while in North America, the movie was released on February 14, 2013. The estimated budget for "Die Hard 5" cost $92 million and its box office cost $304,654,182.