I saw on News.va that today, one year ago, Benedict XVI launched @Pontifex on Twitter.
Pope Francis has continued to use it, no doubt through surrogates.
Here is his latest Latin tweet:
Expers laetitiae nulla concipi valet Ecclesia quae tum videlicet maxime gaudet cum nomen Iesu universis suadet hominibus.
— Papa Franciscus (@Pontifex_ln) December 12, 2013
Benedict XVI is still the Pope of Christian Unity.