The point is much like the Spurs had to transition from David to Tim - Then with with Tim, transitioning from defensive to offensive, the Spurs will have to adapt greatly (IMO) post-Duncan in order to compete. Just trying to sign guys like Gasol/LA to reload if Tim/Manu retire is probably faulty logic and not a great idea.
Would I be upset? No. Spurs would still be a very good playoff team in the West, but it would be a very short-term solution with very limited upside. Spurs should adapt, evolve and do what they have always done (build through the draft) as much as possible. But more than anything, be flexible and adapt to what suits them best.
This is uncharted territory. Spurs, while having FA money before, haven't really had to deal with the possiblity of not having a franchise anchor that makes them a contender if they made the right moves.