Anyone interested in knowing what new ships will be released in season 6 should listen to this podcast.
A quick summary:
Season 6 is all about end-game. The challenges would be tougher, so fleet bases are designed to upgrade fleet member's gear for the new challenges. The upgrades include new fleet ships, fleet weapons, fleet armor, etc..
A properly upgraded fleet base will be able to build fleet ships. There will be a total of around 45 fleet ships to choose from (this count includes both fed and kdf ships). The majority of the new fleet ships will be retrofits of current T2 to T4 ships with 10% more hull, 10% more shields, 10 console slots (current T5 ships have 9 console slots) and a new "sexy" fleet hull material. One caveat. These fleet ships does not come with special consoles that C-store variants have. So you will still have to buy the C-store ship if you want special consoles for your shiny new fleet ship.
* 1000-day veterans will likely be rewarded with a brand new ship class.