So, the premise is this.
In 52 BC, at the Battle of Alesia, Caesar defeated the allied Gallic forces under the command of Vercingetorix, and more or less ensured the conquest of Gaul.
In this case, Caesar is defeated and gets killed/captured. The Gauls still have a strong leader who can unify them, and now the Legions in Gaul are stuck in a very unfavorable position.
What are the consequences, both short-term and long-term?