Although they can release more big ships ffg is fast running out of fighters, they might get another two waves before they are reduced to the really obscure ships.
Now people on these forums have openly said if new stuff stops coming out their interest will wane, a pirate faction gives them new directions staying with rebs vs imps denies them.
What's more I know people that like x-wing but don't really feel an attraction to existing options and more factions would attract them.
People suggesting a broadening of the horizon just want the game to grow and become more popular rather than stagnate.