What's much more likely is that the Japanese police will show up at MtGox headquarters one day with a bunch of cardboard boxes and some kind of bafflingly obtuse misunderstanding and start impounding things, like they did with Mirai Kensaku Brazil. If they're set up properly Mt Gox should be able to survive this, but I hope they've had time to make decent contingency plans...
This morning I woke up to a new high, and to see MtGox is still the biggest exchange.
And.... I thought those Japanese economist brilliant! They will devalue there currency but maintain there balance of payments by creating demand for USD, and people will sen USD to Japan in huge quantities. MtGox is a Japanese Asset.