The emergency responders do not have legal responsibility and control of the aircraft, passengers or crew.
What happens to the pilot would depend on the outcome of any investigation, the reaction of his management and wether he acted in good faith having gathered as much information as possible before he made his informed decision.
What would happen to the emergency responders if they recommended to not evacuate despite being unaware of any situation in the cabin and that lead to a high death toll? What would then happen to the captain?