I just put out the latest numbers a couple of weeks ago... but it sounds about right. Second Life is where the users are.
Unfortunately, unless those users are buying land, then they're just costing Second Life money. Merchants are moving to the marketplace, schools and non-profits to OpenSim, role playing groups are setting up their own grids where they can have basically unlimited land to play with. So the land area of Second Life is dropping fast, and users are declining slowly.
Meanwhile, OpenSim land is growing fast, and usage is growing slowly.
Not a great combination for Second Life. And, at some point, the number of people, and the amount of content in OpenSim will start becoming sizable enough that it will start to snowball. Unless, of course, someone comes out with an even better platform. Which could happen tomorrow. There's a lot of kids programming away in college dorm rooms and parent basements.