Just like a soft fork, you have a long period to inform all the users to upgrade, those who don't care, their software will just not be able to talk to the network and the transactions will be dropped.
That isn't like a soft fork, soft forks don't kick anyone out of the network. And you seem to have missed what I said, because of nlocked transactions changing the transaction format would effectively confiscate some people's Bitcoins.
The world will not collapse because of a bitcoin hard fork, and since it has been advertised as an experiment, everyone knows it can have many disruptions, they all play with risk capitals and will tighten their security belt if well-informed. By successfully doing a hard fork, you cleared the way to many difficult changes in future. You can't spell a new soft fork trick every time when you want a backward-incompatible change. If you have to do a hard fork anyway in future, the earlier the better
If you are aiming for million dollars per bitcoin, it is still very early stage of the development