Caesar's defeat at Gergovia marks a low point in his career and shatters the aura of Roman invincibility. The flipping of the Idui tribe and their control of Noviodunum causes a huge blow to Caesar and the potential ramifications become possible.
With the hostages now in the hands of the rebels, the balance of power and authority in Gaul could shift. The rebels could use the hostages as leverage to gain favor with other Gallic tribes or play hardball against Caesar with their newfound advantage.