We have previously found (and published; Proteins 2002) that RMSD follows approximately an Extreme Value Distribution (see Google on that one). If you were to measure the height of the tallest person in each class of a college, the distribution would also match an EVD. It is definitely NOT Gaussian (normal).
The reason we are alreayd 300,000 times better is due to the approximation - it only approximately fits an EVD. Still, our 'expected' best of 6.16A isnt that far off from the 5.0 that is the 2nd best structure right now. It is great that we can estimate this at all though, as many cannot. This gives us the power to predict how much sampling of a given protein needs to be done to get something good. Another rule of thumb is every time our sampling size increases by a factor of 10 for a given protein, we expect roughly a 1A improvement. Thus if 5A is our best after 1 billion, we expect something close to 4A for 10 billion.

The number of structures any individual has generated is irrelevant. You could theoretically make just 1 structure and get, say a 2A structure. It is like winning the lottery. Just because someone who's never played before buys a ticket and wins, that doesn't mean you should stop buying 100 tickets/week or whatever to increase your own chance of winning Making more structures increases your chance of getting a low RMSD but the important quantity is the TOTAL number of structures made by everybody altogether. As this grows, the best RMSD will gradually decrease.