No, they'd just take their money, exchange it to the other currency (or anything else), and copy over their content (which can be saved with the click of a button).
You don't hear people on Twitter lamenting that they can't transfer over all their wasted time and effort on Facebook. It's just a normal, healthy process
That is not comparable. What do you think starts happening when only a couple whales start selling their steem for the token of this new blockchain? The price per coin goes down, and probably quickly. It will be a similar situation to rats fleeing a sinking ship. The last ones off get nothing.