Mao has already expressed her intention to compete, so I think that takes her out of the discussion. HOWEVER, I think it'd behoove Mao to take a season off to rest and get her head right. She's been going non-stop since juniors--she needs a break! Especially if she's eying Soichi. She can't keep pushing her body like that, not letting up at all...she'll burn out before she gets where she's going.
It's time for another
Good Idea, Bad Idea.
Good Idea: Reworking technique to get correct edges, better speed and more flow;
Bad Idea:
Competing while reworking technique to get correct edges, better speed and more flow...the end (anybody remember that from Animaniacs?

)
I really admire Mao for taking the time to go back to the drawing board but that technique is never going to stick if she doesn't take the time to really learn it. Her flip is the only real improvement I saw last year (she no longer drops her back before taking off, and it had better spring). However, her lutz isn't any closer to being correct and her salchow was often two-footed or UR, and I think she got only one 3A ratified all season long...
I'd like to see Mao take a break next year. Continue to train, but scale back a bit...at least until October. Then she can start training full-out for Nationals, 4CC and then worlds. The key to longevity is knowing how to pace yourself. With two world titles, GPF titles and Olympic Silver, Mao can afford to rest until the big ones role around (worlds and the Olympics). If she continues at the pace she's at now...I don't know if she'll make it to Soichi.
As for Yu-Na, her decision will be about motivation. I think narrowly missing gold this year may be incentive to come back and try again next year; hopefully, she's learned her lesson about debuting at worlds, and she'll test run her programs at 4CC prior (I still think had she participated in 4CC, she'd have won worlds easily b/c she'd have been a lot less nervous).
Still, Yu-Na is very busy. She has a show she's shooting, plus her endorsement deals, the Olympic bid for her country, her duties for UNICEF, her ice show, etc...she's doing a lot. I think last year was a learning year for her in terms of what all she can do. Having won everything there is to win, the only reason she'd need to continue competing is to stack titles...if she wants to do that. The other reason would be love of competition, but I don't recall if I've ever heard her say that. She's reached the mark where anything less than gold is considered failure (a horrible stigma given to skaters who carry a high level of expectation). Anything less than perfection is seen as choking...it's sad but that's the way it is once you're pegged as the "standard".
That's a heavy burden to bear and I don't know if it's one she wants to bear. Right now, there are no elite skaters from South Korea; Min Jung Kwak didn't even qualify to compete at worlds pass the QR. Korea needs Yu-Na to continue until someone decent comes along...however, her obligation to her country has to end at some point and she has to take what she wants into consideration.
IMO, I don't see Yu-Na skating past next year...IDK why, but I don't. I think one more shot at getting another world medal (hopefully gold) is all she really wants...but I could be wrong. I'll just say, I'd be surprised if she goes all the way to Soichi...