More likely to just be another split-season, seeing as the next thing commissioned is a full series of fourteen episodes.
They need to start filming nine months in advance, if they want to get the episodes done in time for broadcast. However, they can't start filming in a month's time as is traditional, or they'd give away a crapload of secrets. So they'll be filming more likely in January, in time for an October broadcast.
Seven eps late 2012, seven early 2013. Plus a shortened gap between series-halves, giving them time to film another series for late 2013.
Or that's what makes sense to me, anywho.