I understand that, I don't believe it can work because businesses will update their software in time, but if someone neglects to do so, it is possible and it can go bankrupt in a second...
If bitcoinXT wins I'm pretty sure we'll see a couple of "legacy bitcoin" holdouts for a while, and for a short time we might also have a good chance to find some smaller exchanges on both chains. So I'm pretty much optimistic about doubling my BTC holdings

. I also expecting to see some bottomed out BTC and inflated altcoin prices as fiat sources can dry out quickly after the first big BTC dumping wave.
This is a plausible scenario, I think the risk for the business is to great for someone to try this, for the business and for the user, in this situation pretty sure someone will try to scam people.