Is it possible Mitsubishi will have to buy back or refund customers money?

The Mitsubishi Mileage Scandal Is Even Worse Than People Thought - Fortune

 

I would say whatever the penalties to VW were, they would be similar or slightly worse. They tend to punish to 2nd or 3rd offenders worse than the 1st one caught even if they did it later.
Also I think it would depend on whether the data they use for the rest of the world is different than that for Japan. That is are their statements about the rest of the world true? Seems unlikely but possible. They may have lied/faked it for Japan but not North America. As I said that is unlikely so they may have massive fines and buybacks plus a further loss of already low confidence/standing in the consumers' eyes.
They almost folded with the last scandal about safety and now this. Quite sad especially with the recent turn around in sales.

last edit i think.
Looking back I have rarely been able to get the numbers they quoted on any of my cars. Yes, cruising on a relatively flat highway I did beat the posted but as far as city I never came close. On the other hand my wife consistently beats the posted mileage in her Santa Fe but could not come close in her Outlander over similar roads.