Or at that age are you doomed to what you already have? I'm 47.
1) The question is irrelavent since you can't be 40 again.
2) Your body usually regresses with respect to muscular atrophy and bone density as you age if you do no weight activity so, yes, you can make gains but even if you could not, you could halt regression.
3) At 47, you are generally a lot wiser and more intelligent than a twenty year old. Brains can win over a gifted dumbass anyday. Coleman obviously has help with regards to brains. However, I infer from the question itself that you may need to work on this area

4) I didn't start training seriously until 40 and stepped on stage the first time at 43 with no AAS or hormone therapy aids other than my young "gifted" wife

I'm 47 and I don't think it's wise to convince yourself that you can't achieve. Just don't follow the routines by the ghost writers in those stupid muscle rags and learn the amount of work you can handle and recover from.