I think mentality is the key in Olympics.
In this case, Yuna is quite strong because she already has OGM, so the pressure is lessen(just my guess btw). She also knows how to handle pressure, and quite surprisingly, she performs well under pressure.
On the other hand, Mao was not able to get Gold in 2010, thus having more pressure from not only her own country, but herself as well. This may or may not effect her skate at Sochi.
I don't know what to say about Carolina. She's amazing, her edges and etc. I've never actually liked her, and her programs, but I found myself kept watching her Bolero
from 2013 Worlds. However, she's iffy... Her 2010 Olympics was a disaster, and who knows if she'll perform like that again or not.
Also, I think Carolina should execute more difficult jumps in the SP such as 3F+3T. Her score from 2013 Worlds was "too" generous for 3T+3T(With a fall).
I would like Carolina to skate to a higher content and deserve a score that everyone can respect.
Anyways, back to topic, Mao and Carolina definitely, but I really think anyone can rival them such as Zijun!!! (love her)
You're smart to mention Zijun, Melon. We have to keep her and the world's other skaters in mind. Though YuNa still competes at an astonishing level, and Mao is gaining more and more command over her jumps, and of course Carolina has many great qualities (though not consistency), there's always the possibility of a dark horse showing up, or everyone else having (Heaven forbid!) a bad night. Remember Sarah Hughes, who never before or again reached the peak she attained on one crucial night.
Just a thought.