DC is increasing the number of characters around Batman.
They have already retconned Damian into a teen to kinda insert more time to him getting older
Eventually I see a point where Bruce will be pushing 50 soon if Rebirth eventually restores the lost time along with the new 52 time
Now most people agree its impossible to do the things Batman does forever. Most people agree the DKR Batman was pushing it to the brink at 55
Of course the character aging is going to just happen anyway. Bruce will naturally age somewhat as the universe ages.
So what if DC inserted a way for the character to just keep going despite his age. Sort of like how the JSA or Deathstroke end up looking
I'm thinking more along the Deathstroke line