The only real goals available in the game at present are character advancement and fleet potency, and the level cap and capital ship acquisition signal the end game in those regards for me.
Unfortunately it is so for now, although things may change if some aspects of X2/3 universe style gameplay are implemented one day. Also i think factions and inter-faction relations have potential to add a lot of extra playability with not so much efforts if used properly. Just some state system aspects like licensing, trade and import/export regulations, technology research/production/salvage bans, etc, and and make it affect player's own development.
Of cause XP-based progressive growth within a fixed still set remains problem for continuous playability of any RPG's, while hard limits on development (like level cap) can really ruin re-playability. Fun thing with SS is that the variety of mods with imperfect i different ways balance actually come quite handy prolonging character playtime. Otherwise the only known (to me at least) "cure" for this is Cataclysm:DDA style skill development (learn/improve by use, degrade when not used, forget if learned to much since, but restore much faster what you already learned once...). Would have loved to see something similar, but don't think it will happen in SS.