yes you are correct !! Only assumption is: Market cap of individual currency touches the market cap of Bitcoin.
Few Currencies have great potential and may cross bitcoin's market cap. (tough it will be a very unusual scenario) but at some point in future, it may happen.

Note : Ofen people talk about many currencies, which can be the next bitcoin, it will happen when price of that coin will cross bitcoin price, i.e. price of the coin multiplied by the total no. of coins = market cap of that particular coin and whenever it matches with that of bitcoin it will automatically cross bitcoin.