To answer your original question, yes your hair follicles have any sensitivity to DHT would result in hair loss over time and the speed and severity is genetically determined. From observation, men without male pattern baldness don't have any temple recession whatsoever after say their teen years. Look at guys in their 60's without male pattern baldness, Richard Gere and David Lynch for example both have a full head hair and the same hairline they had thirty years ago. However I believe that even in men that don't bald they still experience age-related thinning but again, it will vary just as some people get wrinkles earlier than others. Which is why Lynch's hair is slightly thicker than Gere's despite being older.
If you recede to say NW3 at forty and stay their until old age, you still have male pattern baldness even if you don't end up an nw6. The norwood chart isn't about the progression of balding but rather where the hair loss stops for men. A good example of someone with relatively minor male pattern baldness is Daniel Day-Lewis, he's been an NW3 for close to twenty years.