I meet loads of people who have collected coins everywhere. They have 20 different types of wallets with a little bit of value. It's due to happen that people will loose their private keys or forget that they even have an account. Over time that value could accumulate pretty big. What will happen to these 'lost' coins? Will these stay on the Blockchain forever, accessible to no one anymore?
Yes there accounts will be lost forever ; the blockchain lets us know that we should be responsible for our finance so taking care of your private key is so important . Unfortunately like you point out, many people forget their keys and lose their fortune