For a while there, HBO was like clockwork with its renewals, ordering new seasons of shows on the Tuesday after their premieres. But they've gotten out of that practice lately: "Enlightened" had to wait til the end of its season to get the good news, while "Girls" and "Veep" were a few weeks into their respective seasons when it happened.
That said, there was no question that these two shows were going to be renewed, but rather a question of when. "True Blood" is HBO's most popular current series, and while "The Newsroom" hasn't been the critical darling that HBO was expecting, it's still a new drama from an Oscar winner and multiple Emmy winner, with an impressive cast, and that opened to decent ratings last week.
In general, HBO's business model seems to anticipate a second season for nearly all of its shows. In recent years, a couple of new series were initially renewed before the decision was rescinded ("Tell Me You Love Me" because the creative team had trouble conceiving of new story arcs, "Luck" because real horses kept dying), and a handful of others never even got renewed ("Lucky Louie," "The Comeback" and "John From Cincinnati," to name three), but the great majority of HBO shows get at least two seasons to prove themselves, as "The Newsroom" will now be able to do.