Where do you get your numbers from?
I doubt there is 100 000 players in the beta. Its more likely to be something around 3000-4000 thousands.
Just take a look how many that was online on the forum when beta2 was released and we broke the forum record with about 3100 visitors.
As was mentioned above, Frontier announced that they had over 100,000 backers just before the beta process began. They actually had over 3000 alpha backers, so even alpha had more players than you're accounting for.
Obviously that doesn't mean that there are 100,000 players all playing at the same time, but on peak times at a weekend it's probably a fair assumption to say there's between 5,000-10,000 players. So when you take into account that number playing in just 570 systems, it's also a pretty safe assumption that when the full galaxy is open even 10 million players will be more sparse.
There will be populated systems that most of the player base will stick to just for the sake of interaction with others. Hoped You can know that. Or You assume that straight after release every single player will just blitz to unknown regions of the galaxy?
Read back, I did already mention that. The only places you are likely to encounter other players will be the hubs like Earth, which is exactly what we are already seeing in beta with Eranin, and any super lucrative trade routes that pop up again as has already been seen in beta.
But those will be few and far between. Frontier are predicting that the majority of players will spend the majority of their time in the far reaches pretty much on their own.
Given the size of the galaxy, I see no reason to doubt that.
Obviously everyone will want to visit Earth at some point, but there's obviously more profit to be made further out for traders and explorers, and that means pirates and bounty hunters are going to follow those out as well, which really only leaves griefers as a "threat" in tourist locations.