F2P hasn't been out that long, certainly not long enough for the vast majority of the people who came in with it to have reached 50. Give it time, once people get to 50 is when they really decide whether they want to stick around, and thats when you'll see fleet numbers go up. Numbers wont change if people are still all out levelling.
This. There has been a significant increase in the population. They are just spread across the diff worlds. When they reach 50 yes they will be limited, but its that point that most will decide if they are going to sub or not (or buy unlocks). This thread is way too soon, as we've already seen a huge increase in the amt of sub 50 pvp games that are going almost non stop (i'm just assuming the same is true for fps). Give it time.