During this CCC conference from 2011, starting from 00:18:55, the presenter suggests that as bitcoins can be lost (lost private key, dead owner, sending to an "eater" address that nobody posses, etc.), and as the total amount of bitcoins has a known threshold (21 millions), there is a possibility that given enough time, most bitcoins, if not all, will actually vanish (be unusable).
The questions is when?
Actually, according to him:
- if 0.5% of bitcoins are getting lost per year, "all" bitcoins will be gone by approx. 2032;
- if the losing rate is 0.1% per year, it will probably last for a century, but will ultimately be doomed.
And if we suppose that inactive wallets (2 years with no transaction) are in fact lost wallets, we reach that 0.1%/year threshold...