"The 21 million cap means that BTC is designed to be a very high valued currency someday. If a mere 1% of the worlds GDP were poured into it, (690 billion) then each bitcoin would be worth roughly $32,000."
http://www.reddit.com/r/Bitcoin/comments/1c57x1/no_bitcoin_is_not_dead_but_weve_got_some_work_to/