Gotta die for good in the next one
Leatherface can be no younger than 70 by now, and carrying a lot of extra weight. He is never implied to be immortal or semi-immortal. At the end of the movie he is shot three times, stabbed with a hunting knife, takes a chainsaw to the face and sinks below the water while bleeding out, but comes back for an energetic final kill the next day. Even by the standards of slasher movies this is ridiculous. If he gets much older with his history of endless severe wounds he will have to conduct his next kills in a wheelchair.
The movie clearly set up a sequel with the Last Girl coming back for revenge. If he doesn't really die, as in getting his head cut off onscreen or his body literally shredded to bits..whatever.