Entropy increase and end of the universe

What your describing is the theory of the Heat death of the universe which is speculated about since 1850s. However, as explained here, object at astronomical scale are often self-gravitating and that gives them have unintuitive thermodynamical properties like a negative heat capacity. This usually gives more structured systems as entropy increases, and negates the idea of heat-death.

Furthermore, given the fact that the universe is currently thought to be forever expanding and that the majority of the entropy is/will be in black-holes, the estimated time-scale for such thermal equilibrium to occur is huge (of the order of 10¹⁰⁰ years), which gives us vastly enough time to change our cosmological theories about the end of the universe...