There is no end to Kittens Game.
Some of the far off things to achieve in the game include the Cathammer 40k achievement, requiring you to play for 40,000 years. So you still have a bit to go.
The Unobtainium you got is actually only the basis to an even rarer resource, Eludium. It is extremely expensive to produce and can be used to construct certain space structures and research high-end workshop upgrades. Additionally, it can be used to trade with the Leviathans, your most important trading partners during the late-game. They will provide you with resources which are even rarer than eludium and can otherwise only be obtained by massive unicorn production.
To make contact with the leviathans, you need to construct Markers and Black Pyramids.
Also at later stages of the game, Religion plays a huge part, as it grants you extensive production bonuses. You will reset your faith counter often to get a praying bonus, which will lead you to accumulate even more faith and larger bonuses. This is known as the Apocrypha bonus.
Even further, you can sacrifice your apocrypha bonus, by transcending, which is a technology researched late in the game. This opens up even more advanced religion upgrades.
In addition to that, you have the normal game resets, which grant you additional Paragon (among other bonuses). These can be spent on Metaphysics upgrades, some of which are required to open up technology paths otherwise unavailable by non-reset gameplay (as you only earn paragon at a very low rate, 1 paragon every 1,000 years). This will enable you to build the markers and black pyramids mentioned earlier.
Beyond that, there are extremely expensive technologies which currently have no purpose. Their purpose is still to be decided and will be added in later updates to the game; these technologies include Thorium and Terraforming.
It is my understanding that current development focuses on giving more purpose to the Darkmatter resource, a resource that was only recently added to the game.