In the end the client will be decided by the exchanges not the miners.
What miner is going to mine a coin that then can't be sold on an exchange?
you got that wrong my friend, if the miners switch to the new client, exchanges wont have any other choice but to follow, because the old chain will be dead... don't forget, miners are the sole of the network, Bitcoin rely on POW, so having X% of the mining power means controlling X% of the voting power in Bitcoin's network
Well its not quite that simple. Whats the point in having an alive chain and nowhere to sell them if exchanges stubbornly refuse to switch.
Its very chicken and egg.
Anyway I doubt it will ever get that far. Agreements will be made long before the network actually splits.
Dont forget an exchange actually owns 13.5% of the mining power as it is with btchina.