Y'know after getting into Halo modding pretty heavily and learning how Bungie's game was strung together I've come to realize that they don't work with the rigid, structured, easy to patch hierarchical framework you might expect from a well established developer. Their games (I get the sense Destiny is similarly messy) are more along the lines of Einstein's desk. Their code has a lot of eccentricities that make nailing down certain bugs really hard or preclude adding certain features for obscure reasons. It also delivers the gameplay experience we want in a package that runs more than it doesn't. The long and the short of it however comes down to the amount of work something takes to fix. Bungie could start shuffling up Xur's inventory to stymie this leak, but they would probably have to do it manually every week, as patching the system would probably be a lot harder. I can't foresee them taking the time to cockblock a reasonably small subset of their players unless something really exploitable comes up. An action like that would just generate more frustration in a game where the playerbase's patience has already been stretched.
I think they'll probably just keep on carrying on until the next big DLC and then make the next tower vendor they add harder to distinguish from Xur or mingled with his data on weekends or something to slow the leaks down.
The newest patch included a footnote saying that they improved their patching system, so that probably helps. Also, the guy who datamined Xur says Bungie can change him in realtime, no need to wait for patches. He said they can control where he appears and when he appears (as proven during the PSN outage), in addition to that stock pre loading they've done. Someone explained how to read Xur's future stock, I can link it if you want.