I would still call him a 4 yr old based on the fact the rut had started by the time these pics were taken. His neck is not one continuous line to his brisket. It stops short of his brisket in front of his legs. He does not have the neck muscling of a 5 yr old buck either in the rut. How much staining does he have on his rear hocks(if you have pics of him)?
As far as him getting better. Look at the rainfall you had last year and this year. Will you get that rainfall next year? If you like him, kill him. If you think he will get better next year, let him live.