Vitalik said " Casper will make rollbacks infeasible due to its economic finality mechanism in any case.". So there will not be roll back in the future.
I believe him...NOT
hmmm why should one believe his promises ? he has this
on his page
Build unstoppable applications
Ethereum is a decentralized platform that runs smart contracts:
applications that run exactly as programmed without any possibility of downtime, censorship, fraud or third party interference.
These apps run on a custom built blockchain, an enormously powerful shared global infrastructure that can move value around and represent the ownership of property. This enables developers to create markets, store registries of debts or promises, move funds in accordance with instructions given long in the past (like a will or a futures contract) and many other things that have not been invented yet, all without a middle man or counterparty risk.
The project was crowdfunded during August 2014 by fans all around the world. It is developed by the Ethereum Foundation, a Swiss nonprofit, with contributions from great minds across the globe.
and did a rollback.
,back to 300k 
