Based on our current understanding of the universe, the chances of the universe stopping its expansion and collapsing in on itself due to gravitational forces are considered quite low. This is because the observed accelerated expansion, attributed to dark energy, indicates that the repulsive force of dark energy is dominant over the attractive force of gravity on cosmological scales.
The prevailing model for the accelerating expansion of the universe is the Lambda-CDM model, where "Lambda" represents the cosmological constant associated with dark energy, and "CDM" stands for Cold Dark Matter. In this model, dark energy is the dominant component, contributing to about 68% of the energy density of the universe, while dark matter accounts for about 27%, and ordinary matter makes up the remaining percentage.
For the universe to stop expanding and eventually collapse, dark energy would need to weaken or behave differently over time, while the gravitational pull of matter becomes strong enough to overcome the repulsive effect of dark energy. However, current observations indicate that dark energy remains constant or even becomes more dominant as the universe expands.
It's important to note that our understanding of dark energy is still incomplete, and alternative theories proposing modifications to the cosmological constant, such as evolving scalar fields, have been proposed. These theories explore the possibility of a future collapse or a cyclic universe. However, these ideas are still speculative and require further observational and theoretical support.
In summary, while the future fate of the universe is uncertain, based on our current understanding, it appears unlikely that the universe will stop its expansion and collapse solely due to gravitational forces. The dominance of dark energy suggests that the universe will continue to expand, potentially leading to scenarios such as the "Big Rip" or a cosmic future characterized by an ever-expanding and cooling universe.