There are many, many other alternative apps to Aperture. None of them are quite the same, and arguably, none hit the sweet spot between media manager and non-destructive processor quite as well. But they all have a considerable advantage over Aperture now, and that is they have seen continuous development over the past 5 years, while Aperture has seen none. Even if you don't like Lightroom (in either of its guises), it is inarguable that it's tools are, bluntly, 5 years more developed than Aperture's now, and that gap is only going to grow. Among the other alternatives (a non-exhaustive list): CaptureOne, OnOne Photo Raw 2019, Luminar 2018 (which gets a DAM module in a December release), Mylio, DxO PhotoLab, Darktable - these can be used either alone or in tandem with each other. For instance, in LR Classic, you can send your Raw to DxO PhotoLab and return it, if you prefer its Raw processing, and use LR for its DAM capabilities. Almost all of them can be used in tandem with pixel editors like Photoshop or Affinity Photo, or plug-ins like the Nik Collection, or even as plug-ins to each other. While you may prefer to Repair tool in Aperture to that in Lr, there is no way that you can't beat that with one or other of the alternatives.
Translation - I intend to keep using Aperture. Period
Unfortunately, about the only thing that can be said with a degree of certainty is that this won't happen. Even if you don't upgrade the OS past the point where Aperture runs, sooner or later the hardware will give out, and you'll need a new machine, and then you'll be moving to a new app anyway. The difference being that migrating now, with Aperture running, is a PITA, migrating when it has ceased to run, will be a fully-fledged crisis with a severe risk of dataloss.
