I do think that a majority of people will end up moving forward with the characters they have. At the same time i think that guilds and players will face the reality of 25 man raiding in TBC.
I dont want people to underestimate the fact that we are cutting 15 people from every raid team and people are swapping to Pallies and shammies or just race changing (assuming they dont allowed paid changes at the start). You are looking at a shift of a little less than half the total raiding population to be cut from raids and have to go either find or create new groups. That or the doubling of raid teams and logistics to manage them