It depends on. If the deficits are from genetic or environmental issues. If they are genetic, then it could be passed down to the next generation. There are a number of genetic syndromes that can be associated with deficits, but that is not to say anyone with impairments have them. Also, lets try to avoid the word retardation; its become too derogatory. Need to know root cause before knowing chances.
It depends. There are some causes of mental retardation that can be hereditary and many causes that are not inherited at all. It really depends on whether there is a known cause- for example, birth trauma would not be inherited but certain metabolic disorders can be. If you have concerns about your child's development, have him checked by his doctor.