Assuming you have $5000 worth of Bitcoin that's 25 bitcoins at the current $200 exchange rate.

So bitcoin has to go to $40.000 for you to become a millionaire.

Bitcoin at launch was $0.05. So value of bitcoin has doubled 12 times since launch, and the value of bitcoin has to double 8 more times for your to become a millionaire. So that's quasi-plausible. Not holding my breath, though :)

[1] Source https://docs.google.com/spreadsheet/ccc?key=0AmcTCtjBoRWUdHJ...

"At launch" it was worthless.

So take a decision now about when you'll sell, write it down, and stick to it. Mine has a 5 year timeline, or a specific value (a few orders of magnitude more than today) at which I'll sell.

"When the facts change, I change my mind. What do you do, sir?" --JM Keynes

:-)

If bitcoin replaces the dollar as the unit of account, currency of international trade, world reserve currency, and so on, it might be better simply to spend the bitcoins than to "sell" them.

If that ever happens, our homes are gonna be visited by flying drones. But you don't need that to happen for Bitcoin to make you rich. It could very well just stay as a high value, scarce commodity. A few whales buying in can make it happen.

If you currently held 0 BTC, would you spend a few thousand dollars on BTC now in anticipation of huge price increases later?

That's the rational way to see it. Then again, what would you invest in at all thinking like that?