A mythe about BTC : BTC dissapeared

[anna.murphy]

I will explain why BTC won't disappeared.
If one day someone gain a great power in computation we will all switch to more secure address. This guy will guess the private key of all the BTC that were not moved to new security system. So the lost BTC will be reintroduced into market.
But this hypothesis is true only if there is not a limit in computation power.