I used to fear the same. However better technology/protocol is not enough to replace bitcoin. There are way better Protocols for messaging than SMTP, so why haven't we moved from e-mail?

Also, with services like https://shapeshift.io/ I can forever hold only bitcoin, and can pretty much instantly convert it to whatever other alt-coin I want. Lets say there is indeed a future encrypted-coin which provides perfect anonymity and perfect security and blah blah blah. Cool, I want to use $1,000 worth of encrypted-coin to buy some stuff, so I'll just convert my 0.01 BTC (or whatever equivalent) and do that.

I believe shapeshift has an API too, so it will eventually be even more seamless to "convert" among alt-coins. Might even be transparent (send XX bitcoin and it'll automatically be received as whatever coin).

So, When everyone knows bitcoin, and bitcoin has the largest market, and is the original cryptocurrency, and has the most infrastructure, and the most developers, and can already easily be converted into any alt-coin; Tell me, what is your best argument for how something like Monero will surpass bitcoin?