Bitcoin has applications for which it is uniquely suitable. There lies its potential IMO, not in competing with existing currencies and payment systems.  It will enable new business models that could not have existed without Bitcoin and that will depend on Bitcoin.  I agree that it may remain a niche currency, but I don't think it will ever disappear completely. Or a least it will be replaced by another p2p cryptocurrency.

It is very hard for us to imagine today what those business models might be, just like people could not have imagined in 1990 that Facebook is a viable business model.  Perhaps Bitcoin will even evolve into something whos prime use isn't a currency at all.  

As for the dot com bubble, the "new paradigm" did create real added value, this just took a longer time than most people expected, and the added value was grossly overestimated.

If you had invested in the right companies you would have made money.