It says absolutely nothing. If you look at the top altcoins when it comes to their market cap, it's just the fact that pure manipulation makes their price (and thus market cap) go up higher than ever. The majority of the circulating coins from each top altcoin are in the hands of a very tiny number of people, and thus they can basically keep buying up their own coins continuosly and push the price up even further. In that regard, I wouldn't be surprised if more altcoins in the future will hit the $1 billion market cap, while the current top market cap coins will most likely hit newer highs.