Really, how much speed can one improve on if their edges are so great? Her speed can improve but the improvement will eventually stop if her edges doesn't improve. Speed won't really cover her other flaws. To improve her edges would mean Caroline is going to have to splat for a bit. The coaching change is good by all means but going to a big name coach doesn't mean you'll start winning. If Caroline earns her spot to Vancouver, good for her but IMHO, she'd be more ready for Sochi after she fixes everything.
Caroline is in a prisoner's dilemma, sort of. If she goes to someone like Don Laws, she's going to have her technique fixed but it means she most likely will have to sacrifice this season because there's just so much to work on. If she chooses not to (given the possibility of what happens if she does), she really isn't going to be posing a challenge to Mao, Yuna or Joannie because her technique issues gives away points despite the fact that she has skated the most splat-free-mistake-free (physically, not on paper) free skates last season.
I do agree with several posters who said that this summer's coaching changes is like a last ditch-effort. If X skater had the goods going, changing coaches isn't necessarily a bad thing but very few skaters can be like Shizuka who changed coaches during the Olympic year and win. That said, for Shizuka, her faults consisted of a lip and motivational issues, which the judges looked passed the first at the time anyway.