As old time MS-DOS loving Never Appler, I don't get this. Every few years, if I need a new computer, I look at the options and then I buy or build one that meets my needs.

What does it matter if the vendor is going to, or not going to, offer a similar-but-updated one in a few years?

Well, if you're investing time and money into a platform, you don't want to waste it on a dead platform.

I'll use myself as an example. I've written some scientific visualisation software, which uses OpenGL. It uses Qt and works on multiple platforms, including FreeBSD, Linux, MacOS X and Windows. Should I continue to support MacOS and invest in Mac hardware to do so?

Right now, Apple have just deprecated OpenGL; maybe they will drop it entirely in a few years. Their hardware is anæmic, with low end GPUs and not much memory. I'm not going to invest in Metal support given the lacklustre hardware support for high end visualisation. I'm also not sure I'll have that many users on the platform, particularly if it doesn't get some serious improvements. You can order or build an excellent PC and run the software on any other operating system of your choice and have it run circles around the Mac in terms of performance and capabilities. So on balance, I'm retaining support for the moment, but I will almost certainly drop it in the next year or two unless they up their game.

Sad really, MacOS X was wonderful a decade back. Today, it's an outdated and poorly-maintained, buggy mess. And the hardware story is tragic.

That is a different context. As a consumer I don't care about OpenGL. Developers will support whatever newer APIs Apple comes out with depending on their sales numbers. Its a simple cost/benefit.

As a consumer, from a long-term perspective, I would never choose OSX because it has no history of backwards compatibility. So I would never choose OSX for running my line of business applications.

I don't agree that it's a different context. An end user might not care directly about OpenGL or any other low level feature, but these things will directly affect the availability and quality of third-party software for the platform, and hence factor a consumer's decision about which platform to invest in.

Okay, I'll go ahead and agree with you that it can be a factor. My opinion is that it is an insignificant factor for a person in a store buying a computer.

I was a die hard Microsoft lover for many many years.

OSX is a much better operating system than Windows.

So Im stuck with buying from Apple and Mac Mini was their entry level cost machine, that's why it matters.

Nitpick: I always hated Windows, I've used Linux for the last 23 years.

But I still don't get it. Suppose in two years time, Apple axes the Mac Mini; but today the mini meets your needs. In three years time, you will have to shop around for whatever MacOS supporting computer meets your needs then, but you'll have to do that regardless of which Mac you buy today.

Now it might matter if you are considering switching OSes. I.e. you fear that in a few years time, MacOS will support no computers that meet your needs. In that case, you might consider making your peace with Linux (or even Windows!) today.

I've tried all operating systems that took my interest.

For my purposes, and by my personal measures, OSX is far and away the very best OS out there. I therefore will buy whatever computer I must to use that OS. Nothing else matters to me.

But realistically, when has Apple guaranteed anything about future products? Even if they released a newer version of the mini, you might hate it because they changed something you like.