Tatiana Totmianina is probably planning to have gallbladder surgery after Torino. She has had two debilitating gall bladder attacks over the past two months.
However, I wouldn't make any assumptions about which teams make the podium when there is a vacancy. Ice Dance can be very political, and who knows who the next "favored" one will be. Grushina/Goncharov, for example, may well be "promoted" to World Champion this year. Then they will likely retire. Delobel/Schoenfelder have also mentioned that they may not continue past this year, so they, too may get a podium spot.
As far as Belbin/Agosto are concerned, I am not assuming they are a shoo-in for an Olympic OR World medal, and it has nothing to do with their talent and ability. They ARE more than good enough, but as we know, ice dance judging can be downright peculiar.
In Pairs, just because TT/MM are retiring doesn't mean the Pettikhs will retire, too. They want one more World Championship, and I wouldn't be surprised to see them hang around for another year.