The Old Republic is releasing a mini-expansion, Rise of the Hutt Cartel. It costs $10 for subscribers, and $20 for non-subscribers. It has 5 levels and a new planet.
Sadly, the class stories are not continued, with only two storylines, Empire and Republic being offered.
The real question, in my mind, is how will this mini-expansion interact with the current endgame. TOR has built up a fair chunk of PvE endgame by now, and I can't imagine that this small piece of content can totally replace that. At best, I expect one or two flashpoints, and one operation. That doesn't sound like enough.
Maybe the power curve will be very flat, allowing the current endgame, or at least the latest two operations to stay relevant.
Still, this will be an interesting experiment.