CBS has ultimate control of the ship featured in the game, yes cryptic are allowed artistic license for the designing of their ships but ultimately it's the big boss heads at CBS that have the final say, that said I have heard a rumour that the Vesta Class is on it's way, don't ask me where I heard it I can't for the life of me remember, all I remember is hearing it and jumping around the room.
Only the Devs or CBS can answer the question of where they are, but alas the devs are secretive with their ships and for good reason CBS can be right pains in .... yeah you get the picture.
Vesta came from a novel and CBS has been trying to get the okay from there.
That Said: The Vesta has been on hold since the first mention of Cryptic sayin' they were conferring with CBS to get the Vesta into STO. There's a lot of people wanting the Vesta in. But so far, no luck.
The likely hood of a Sovvie refit is more than likely going to happen. All you have to do is look at the current way they are making the .5/+1 ships. (link to the ship chart http://www.spidermitch.com/STO/Spide...DShipChart.jpg ) It looks like every class of ship in the game that isn't already a CStore ship will be getting a refit. There's still two Commander level ships to be released, Cruiser and Science and before anyone nitpicks that just look at it as a CStore variant if you want for the Nebula and Excelsior Class much akin to the Vulcan Science vessel and the Captain level tactical ship the Sao Paulo class. I'm pretty sure that the RA levels will be next too. The Galaxy Dread is moving up to VA level and I think I read somewhere that the MVAM Prommie is moving down to RA level to act as a refit/.5/+1 ship. Now if they (Cryptic) where smart the could save themselves some time and money and take the already existing CStore ship skins for the RA level ships and just make them the .5/+1 ships. (As long as they grandfather in all of us who already own those skins) Just add a new console exclusive to each and tweak the BO load out. I also wouldn't mind if they actually came up with something new either just as long as they can use the non refit class skins like they do now.
Example: The Sovvie Refit would come with a Console to give it a rapid fire Quantum Torpedo effect like in the movies and give it a third tier tactical skill (Lt. Commander) opening it up to Beam Overload 3 or Torpedo High Yield 3. One must also keep in mind this ship was made to have more powerful weapons and shields which cost it in speed over all.