For me, Don's future goes like this - yes, he goes back to New York and writes the famous Coke ad.
But he's also had an epiphany about what a ****ty father he's been, and with Betty dying, he's determined to change that, and be a real father to his children.
The line that was said to his niece about "your child will wait every day for you to walk through that front door" hits home with Don, as does the guy in therapy that Don hugs when he recognizes himself in what the man says.
bold=yes
the rest... NOTHING in Don's character suggests that he could POSSIBLY do any of those things... you are just wishing...
hey the niece leaves because she knows she is not gonna do ANY of the things that the world (or esalen) expect of her and she just has to own it...
Don is Don. He is an ad man. He is always looking for the next drink, lay, moment of sincerity that only lasts a moment. He wishes he was different, but he never will be... most people aren't.
Think of every person you have ever known... they NEVER do anything that involves a complete change... this is why addicts can never become social users... it has to be all or nothing. Don is never going to be a good parent, husband or even employee. He will be a great ad man though... and so, he does that... just like the rest of us..