The series is very early on in development at the moment, and little is known about the details of the show: Will it be an ongoing thing or a one-off miniseries, when it's going to air, or if any other 24th century characters might also return. We do know it's going to be set about twenty years after Nemesis (so getting close to the 25th century), and in the US at least it will be released on CBS All Access. Here's how Stewart summarised it at STLV:
He may not, and I stress may not, be a captain anymore. He may not be the Jean-Luc that you recognize and know so well. It may be a very different individual. Someone who has been changed by his experiences. Twenty years will have past, which is more or less exactly the time between the very last movie, Nemesis, and today.
We have no scripts as yet, we're just talking talking talking storylines. It will be, I promise you, I guarantee it, something very, very different. It will come to you with the same passion, and determination and love of the material and love of our followers and our fans, exactly as we had it before.