I've heard it said that no more than 10% of the player base is on at one time. Take into consideration the trial players, the long timers who don't play much, and all of the current active players across the planet, and numbers in the thousands doesn't seem all that unlikely.
I notice one of my rankings, captures, is up around 3700. I have no captures, and imagine that there are more than few players who don't have captures, so that could mean hundreds of people tied for that rank?
I believe I saw over 600 logged in over the weekend. During a weeknight in the fall, I think it's normal that peak numbers are down somewhat. The problem with trying to justify or argue against any sort of change with just the arena numbers, is that that's the only figure we can see. HTC, OTOH, has access to all the numbers, all the trends, all the cancelled and reopened accounts, etc. This bbs is an overwhelming minority of the player base, whether we choose to accept this fact or not. Saying, a majority of people support idea X, without any sort of figure to validate that statement, holds about as much water as Krusty's claims.