You're right, but there is more to the picture.
Certainly until relatively recently there have been 3 theories. The first is that the universe is expanding rapidly enough that gravity will never "take hold" and force a collapse. However, rate at which the universe expands will gradually reduce due to the action of gravity on all the matter in the universe.
The second is that gravity will take hold and cause all the matter in the universe to collapse back on itself. We could potentially get another big bang event or whatever at that point, it's unknown.
The third option is that there is exactly the right amount of matter so the universe "just" stops expanding then sits there, in balance.
Until the late 1990s these were the accepted possibilities. Recent observations of a certain supernova type have shown us that the universe is expanding
at an ever increasing rate. This is a very significant result.
The implication is that there is some additional force that we cannot currently explain which is acting against gravity and pushing the matter in the universe apart faster and faster.
The clever particle and string theory guys call the cause of this force
"dark matter".
It's highly significant, and probably the most exciting development in modern physics in the last 20 years. It will be huge when we figure out the details.