My 8 year old son has been diagnoses with ODD and ADHD at the age of 4 to 5 years old. I was told by a family member that this diagnosis guarantees that he will be diagnosed with antisocial personality disorder. Is this true?

Not true. None of those diagnoses are etched in stone anyway. They have been invented as a handy way to be covered by insurance. I trust you don't pigeonhole your child.