This is a really good point. The only explanation I can come up with is that while past purchases are at least visible to those that bought them, it could be th

This is a really good point. The only explanation I can come up with is that while past purchases are at least visible to those that bought them, it could be that when they try to install it, they'll get an error prompting them to alert the developer that it needs to be updated. This seems like a poor UX, but I can imagine someone inside Apple pointing out the optics of removing folks' past purchases in the context of the current "only one app store" debate, so this might have been a compromise they settled on. If this is the situation, one way Apple could make it seem less egregious is to space it out over time by performing the culling of apps now, and altering the SDKs in 6-12 months or so, which would then trigger the breakage for past purchases. Folks will feel comfortable defending that because everyone had warning that change was afoot, and they'll likely make the the case that users that lost their old apps can't expect them to work forever. Or, in the words of this post, "old apps sometimes die".