When writting it is hard to see a chord as a suspension until the next chord. Simply because a suspension a note in a chord that is temporarily replacing a chordal tone and the resolves by steps back to that tone. The difference between a chord like D5/A and Asus4 is the D5/A is free to move just about anywhere. An Asus4 will next change to a Amaj chord, or A5(less common). Hopefully this makes sense.