Daybreak have announced that they will be lowering server capacities in an update tomorrow. We know that the current maximum server capacity is 200 but they have not specified by how much they are loweing this number. Here is what they had to say about the change:  

Hey everyone

We have noticed in the past few days that performance has been taking a hit on the most populated Just Survive servers. We are going to be making a few changes on our end that should boost performance across the board. There will be some minor downtime tomorrow (5/19) at 3AM as we roll out these changes.

In an effort to reduce KOS and crank up the zombie fear factor we are going to be lowering the max player cap per server. This should make encounters with other survivors a little rarer while still keeping the high zombie count. This will come with the minor server downtime. These changes might cause you to see longer than normal queue times at peak hours.

Source: Reddit r/h1z1