In a dark cave with 2,000 people, the collective light they emit would not likely produce a visible light source on its own. The reason is that the amount of light emitted by humans is very small, and individual human bioluminescence is not visible to the naked eye under normal conditions.
While some organisms, such as fireflies and certain marine creatures, can produce visible light through bioluminescence, human bioluminescence is extremely faint and not visible without highly sensitive equipment.
To create a visible light source, you would need a much larger number of people, or you would need to rely on external light sources, such as flashlights, torches, or other artificial light devices.
In a pitch-black cave with only 2,000 people, the darkness would remain, and the collective light emitted by humans wouldn't be sufficient to illuminate the surroundings significantly.