Again, if they don't control 51%, their new statefile would be pointless, unless they did a hard-fork, but if I have the resources for a 51% attack on the curre

Again, if they don't control 51%, their new statefile would be pointless, unless they did a hard-fork, but if I have the resources for a 51% attack on the current fork, chances are I have the same capability on the new fork. The only way what you propose would work would be if they could cobble together enough resources to break my 51% control. So BTC would go 100% bust if someone managed a 51% attack. The question is, can someone with 1 transaction of 51% get enough converted to USD/etc before enough people noticed. Otherwise the financial incentive isn't there to try. I'd guess no matter what, it would be a huge fricking mess and if you did it in a country that didn't like you, it probably wouldn't end well for you years later when whatever govt you live in gets around to ruining your life, even if you managed to extract a few billion. Because you know the exchanges like Coinbase as soon as they noticed would do their best to stop you(as it's in their best interest).