ladybug - I believe all Federations will pick their respective teams for the worlds. If it is dependent on the results of their respective Nats, the Federations, imo, wil ensure that the results of the Nats will reflect their choices for the Worlds.
However, the actual placing of the skaters will be the opinions of the judges.
Imo, Cohen was the favorite in last year's Nats, (and Worlds), so she had to be included in the mix of the Nats placers.
For this coming Nats, Kwan and Cohen will be in the top three at the Nats so they can be in the Worlds. I believe AP is due for the third spot. But this is just the US Association. I also believe the Fedeerations of Japan, Russia and Canada will also pick their top three before the worlds.