the expected appreciation is unknown...
but the facts are;

- there is a limited amount of coins that will ever exist. (aprox 21 mill)
- centralized banking has proven to do anything to protect its own currency (EG Cypress)
- as time goes on it will get harder and harder to mine the remaining bitcoins

As with any currency , value = trust.

If it gets going, whats to say a government wont run a big fear campaign to destroy the trust people have on bitcoins.

My advice, just buy what you can afford to loose, and enjoy the ride!