That would depend on the exact nature of the format. A lot of people are speculating that it will be a new unlimited-like system that just starts at BW, and if that's the case, prices will probably drop slightly after rotation, continue dropping slightly throughout 2014 (based on power creep), and then have another big fluctuation around the 2014 format change once the details of the new format are released and how many people decide they're going to participate in it.
If the format ends up being something entirely different than what people are expecting, the pricing will probably start out similar, but the fluctuation at 2014 format announcement will probably be more pronounced. If it's something gimmicky, or if it doesn't get a lot of support (very few tournaments using it or lack of CP for participating or whatever) prices would probably drop quickly due to people deciding to not even bother with the format, even if they thought they might like it before. On the other hand, if the format is really cool, or if it offers something new with very heavy support, prices might even increased based on more people wanting to get in on it than planned. I don't think either of these scenarios are particularly likely, but they're possible.