Wait.... bitcoin cap is 21 million, which puts the 100 billion cap at 4761 times that of bitcoin.
The market cap is their value measured against the US dollar. Bitcoin is at 10 billion at the moment http://coinmarketcap.com/ If dogecoin rose to 100 billion ~10 the size of bitcoin each coin would be worth a dollar.
Wait... now that I read the above comment again, I think you may be right... they are saying that it would only take the total value (market cap) of dogecoin to be 8 times the current market cap of bitcoins for the dogecoin to be worth at least $1 a coin.
So nevermind, you are right and I was wrong. In my defense, the original comment was a little unclear about what they meant.
I don't see it happening, and I don't even see the Dogecoin market cap even reaching the Bitcoin market cap, at least not unless Bitcoin itself becomes a major currency, and Dogecoin becomes the official joke currency.