If you look at the arc of the show, they have already "ended it"..
Don has morphed from the hunky man with a deep dark secret, and charm-galore into a middle aged, creepy womanizer who trashes everything he touches...even his secret turned out to be not as important as he thought it would be.
Sally has grown from an impetuous child into a thoughtful young woman
Betty is what she always was..shallow, vapid and unhappy..but even she apparently plans to go back to school, so maybe she will end up in a better place
Joan transformed from the va-va-voom dish/secretary who was a joke, into a woman with power..and she had a child she loves....
Peggy also moved up the ladder and wants to become "Donna Draper". She was a timid mousy little character, but she's definitely not that any more.
All the other characters were always peripheral, so their changes are not all that much.
Mad Men (to me) was always a trip though a life..our own
We all make changes that, when we look back, seem huge, but since they happen a day/.a person at a time, we don't even notice them