And there is no binary choice here. Apple can, should and will monetize Siri with consumer tracking, AND they will add capabilities in order to get more sales and more profits by inspiring repeat purchases by their customers.
Customers are tapped out and cutting discretionary spending left and right, besides we already have Google and Fb to fulfil our "consumer tracking" needs. As this sort of targeted advertising becomes ubiquitous, the ROI diminishes. Tell me, how's that Fb stock doing?