It is very important that every exchange is ready for the transition. That is, prior to the release of 2.0, they disable deposits and withdrawals, then they do the 2.0 transition, and then they reenable deposits and withdrawals on the new chain.
That way there is no exchange accepting or trying to give out BTS tokens from the 0.9.2 chain.
If this occurs, no one will be able to dump worthless old bts on unsuspecting people, and there wont be a division between people who got screwed and want to make old BTS worth somehting, and everyone else.
Most importantly we need poloniex and btc38 to follow this. I am pretty sure CCEDK will since they are a partner. I dont think there is much BTS on the other exchanges anymore. I bet at least one of bter, bittrex, and cryptsy will fail in some way in the 2.0 transition, but it will mostly just be a black eye for them.
You probably want to avoid trading of those IOU tokens aswell because otherwise people would transfer days before and dump right after genesis block (people who create genesis block and their friends get first dibs) and then they can sit and wait until withdrawing is enabled again to get free BTC out.
With PTS it stopped at the time of the snapshot... instead it would be better to stop a long time before.. and a few hours after everything is done.