The far future is truly Lovecraftian and hard to fathom. Eventually star formation will cease, most of the timespan of the universe will be the "dark era" where black holes slowly evaporate due to Hawking Radiation. Then there will only be light, and when there is only light then time itself ceases to exist as a meaningful construct. Space, too, perhaps. Then there is an alternative, even longer ending, if it's possible for light itself to decay.

Semi unrelated but I really love futuretimeline.net for stuff like this. In the shorter term they try to make predictions on a human scale but the extreme long term is all astronomical stuff since it's the only thing that can be predicted millions of years in the future