Yeah, I don't think anyone is pushing TP out the door. It's just that the Spurs could be re-made without him if trading him brought something of close to equal value.
Spurs used to live with 4-down until Tony matured. Then the Spurs started playing a spread the floor attack because TP could penetrate to shoot and dish so well. Both styles worked in their day.
TP has alot of good years left, but he will be on the downside of his career within the next 2-3 seasons. Considering how to adjust the attack strategy for the future only makes good sense.