People who are deaf aren't using the parts of the brain that would be devoted to processing audible information. That part of the brain is free to be devoted to any other task. I think its entirely possible that that unused brain anatomy would be employed by other senses whether that is sight, or smell.
I do believe that when one sense, such as deafness, fails, one or more of the other senses increases in an effort to try and compensate. Blind people have a sharper sense of hearing, which their bodies may have gradually increased in an effort to compensate for the lack of sight.
People who lose a sense have often suggested that their other senses are stronger, so I would assume that this is true. I believe losing a sense gives the brain the opportunity to further enhance the other senses. This gives a person the opportunity to experience these sense more fully and it should help them in their daily lives.
Yes, deafness does increase some of the other four senses. This is a known fact. It has been documented and verified by doctors and scientists. People who lost their hearing later in life will also report their other senses heightening after the fact. This is very interesting and I find it fascinating.