Is it possible that i could become a vegetable if the surgeons make a mistake during the temporal lobe surgery?

Unlikely: If you are being treated in a major neurosurgical center, by a surgeon with a good reputation, the risks will mostly depend on why the surgery is being done and how serious is the problem, i.e. Epilepsy, benign brain tumor, malignant brain tumor, etc.

Not likely: Your risk of major neurological deficits depends on the extent of surgery. Small lesion versus large, deep versus on the surface, among other factors. Surgeon experience is also important. Ask important questions about risks, benefits, outcomes before you commit.