The majority of the new fleet ships will be retrofits of current T2 to T4 ships
All of them or just some of them?
[crosses fingers that its all of them]
There won't be fleet versions of the Constitution, NX or Oberth as they are Tier 1 ships. There also won't be fleet versions of the Excelsior or Galaxy-Dreadnought. I am not certain about this but for the Federation, only Starfleet designed ships will have a fleet version so this excludes the Vulcan D'kyr and Caitian Atrox.
Generally, ships that are sold in the c-store and come with a special console in the C-Store will have a fleet variant. While I understand the financial reasons, I do wish they would give an in-game reason for this decision.