She began losing her hearing at around 15 months old. It was moderate at 18 months but moderatly severe by 3. She is 7 now and bilaterally implanted. Our surgeon will implant if the child has a greater than 70 db average loss and isn't making appropriate progress with spoken language, and your son clearly isn't.
Will he start suddenly speaking....I doubt it. Kids who are early identified and early amplified are usually caught up by age 3, not non-verbal. Clearly what you are currently doing isn't working. He is 3 and doesn't have language, something needs to change.