For a start I predict it will cause all exchanges to "stop trading" (as they will not want to risk fiat losses in case they have ended up on the wrong fork).
They are in it for profits so why wouldn't they just allow trading between the two different chains and make lots of fiat money in the process?
I guess the obvious answer to the above question is that most exchanges are inept.
Surely that would not be possible. Won't some transactions appear in both chains, and some old bitcoins be spent in different transactions in each chain. Am I correct in assuming that only the longest chain will survive? What will happen to the shortest chain additions? Will they be deleted and the process start again?
Here is another newbie question? If one chain contains blocks up to 1Mb and the other contains all those blocks plus the 2Mb blocks, won't the 2Mb chain be longer no matter who accepts the proposals?