Although we've been able to increase our ground attributes and equipment, the same is not true in space.
Although we could increase the level of some of the higher level skills, the ship has remained a Tier5 level.
In essence, we're essentially playing at RALH level whenever we're in space.
Will there be higher tier ships one day?
Personally, I'd prefer that the hull level, power levels etc increase to match your rank, so your ship "evolves to a tier 6 and so on when your Rank increases.
That way, you get to keep using your favorite ships and have the bonus of them becoming more durable in battle as you advance through the ranks.
D.Stahl talked about rising the rank cap to fleet admiral at a later point in a interview.
He also said that we'll gonna get tier 6 ships to match the new rank, but we probably not gonna see that until the season 5 patch or even later.
There also a Vulcan D'Kyr Cruiser coming some time in january and an Andorian ship in february, not sure about their class or tier tho.