It's had a good run, but it's almost over, the Pope's Twitter account is going down along with the Pope himself. Apparently, the account will be shut down after Pope Benedict XVI leaves office next week.
The Pope has announced he will resign his role, something that hasn't happened in a few hundreds of years. There will be a period during which the future pope will be sought, but in that time, no one will be using the Twitter account.
The Vatican doesn't believe such a powerful communication tool should be used by anyone but the Pope and, since there will be no Pope at the Vatican, there will be no Twitter account either.
It makes sense too, while the account is registered as @Pontifex, along with several other handles for tweets in languages other than English, and not in the name of Benedict himself, it has been designed and used by him exclusively.
That said, the Pope was able to amass a huge following very shortly after his first holy tweet, he has close to 1.6 million followers on one account, so starting a new account for the next Pope shouldn't prove that difficult.