Principles never change! In early years of evolution, people were God loving and gave out some sayings which are based on moral. Moral has no age, hence all those which you brought out will be always applicable even 10000 years later from today...Those days all worked for the combined uplift of society.
You can't find an alternate for TRUTH! TRUTH will remain same irrespetive of the period. We breath through nose, eat via the mouth, hear with the help of ears, feel the touch coutesy the skin, taste is the tongues ability! Will or can they ever change?
Modern thoughts are selfish oriented for betterment of self or close friends & relatives. So these thoughts will vanish and will not be sought for any reference! May be a few odd court cases may come in for reference! Otherwise even modern thoughts which are articulated around TRUTH will certainly find a place in future references!