There's no doubt that it's still popular with certain audiences: the queues for the Friday night evictions at the studios testify to this, but after ten years, the format is a little tired and the production team are deliberately looking for more outlandish contestants to keep the ratings up in the UK. How the other 41 places around the globe are faring is anyone's guess!
Endemol's site states:
Big Brother is all-seeing, all powerful and getting even bigger across the globe. There is no limit to the Big Brother phenomenon.
Well, maybe there is a limit, we'll just have to wait and see.