Bandai Namco has now commented on how old Heihachi Mishima is in Tekken 7.
Katsuhiro Harada revealed on Twitter that Heihachi Mishima is “over 75” years old in Tekken 7. In Tekken 6, he was exactly 75 years old. Many of the other characters in the game don’t look that much older. It’s entirely possible that Tekken 7 takes place only one year after the events of Tekken 6. This could mean Heihachi is now 76 years old.