I feel sorry for Tony as he was "the baby" of the big three. So, when he saw Tim and Manu effective in their late 30's he probably assumed he'd last that long. But now in his mid 30's, he may go out a season or two after Duncan/Manu.
Some of this statistical decline, though, is Tony is not being asked to do much to a) keep divas LaMarcus and Pau happy, b) allow Kawhi's leadership to grow, and c) preserve his body. As I said in an earlier post, I think Patty should stay with the second team. So, the question will become is our third string PG better than Tony? Is Nico, Forbes or Murray ready? I have to say no. So, for now, Tony should stay right where he is. Long term, who can say. I suspect Tony's role will continue to dwindle until he retires or asks for a trade or gets the Bonner/Horry/Bowen treatment. (Bowen as I recall his rights were traded at the end).
Anyone remember how Pop dealt with Elliott or Avery at the end? Were they forced into retirement? I can't recall.
Manu will be another interesting ending. We expect this to be his last year. But if he chooses to come back will he be worth 14 mil again? Eventually he'll only be worth a low salary. And, if so, will he take it, retire, or take the money from some other team for one final awful year in Philly or somewhere else?
My hope is both Tony and Manu retire as Spurs. I give it only a small chance that both do so.