There are few concepts as truly badass as an elderly Bruce Wayne. The old guy that you don't mess with at all. Old Bruce is older, wiser, and could break you in half.
There are few images more compelling than an aging Bruce Wayne taking on one last mission. Bruce technically a child when the Mark of Zorro appeared in the theaters.
The Mark of Zorro was a real film that starred Douglas Fairbanks and premiered in 1920. Bruce looked about 12 at the time.
That would mean that Wayne was born essentially around 1908. If he were alive today, he would be a grizzled 104 years old today. Jones is theorized to be about 111. It is entirely plausible that a fictional Wayne still could be alive. For the record, Dick Grayson would be in his early eighties. Of course, they may be a little forgetful as well as more than a bit punch drunk.
Even Bob kane theorized on what a badass character an elderly Bruce Wayne would be. Kane was not particularly a fan of the depiction in The Dark Knight Returns. Kane actually believed that Wayne would age more like actor John Forsythe.
Of course, these days we also have an idea of what an 80 year old Bruce Wayne might actually look like.
While the Dark Knight Returns may be the most famous example of an elderly Batman, it is hardly the only one.
In 1996, Wayne appeared as a counter point to Superman in the futuristic Kingdom Come. Wayne assembled his own group of supe heroes. They were mostly younger and more inclined to view Batman's vigilante ways with honor.
The animated Batman got the older treatment as well. Wayne served as a mentor to the new Batman Terry McGinnis in the television show Batman Beyond. The show spawned one of the great Batman movies of all time Batman Beyond : Return of the Joker.
irregardless, the image of Batman's life continues to inspire old and new generations. Inevitably, an aging Bruce Wayne has become an increasingly vital part of a continuing mythos.