Lower power consumption would be nice too. We don't always have mains power.
I can go to Mouser right now and buy a pin-compatible 80186 right now in quantity of 1. You can even order a new 8088 from Renesas, but it says they're back-ordered til next February.
I've seen 386s and 486s manufactured recently enough to have the "newer" Intel logo (the one without the dropped "e") which implies well into the 21st century.
With modern product lines, I'm not so sure. The Atom-class products that seem most appealing for embedded use tend to have a very short shelf life (in those terms). I wonder if they're saddled by a dual market obligation-- I suspect Intel wants to sell to both "quantities of 100" embedded markets, and "quantities of 100,000" $199 laptops/tablets, but they're really only viable use of production capacity as long as the quantities-of-100,000 orders last.
I'm not sure the ARM ecosystem is better, because of the tendency to highly-integrated SoCs. Even if some manufacturer says "here's a vault with 50 years worth of chips", it's unlikely they'll have the one particular part you want in that vault..
I wonder if, of all things, it would end up being something like the RP2040/RPi Pico. Third party designs are going to leave a lot of inertia to keep it available as-is, and at the same time, there's not really a single market-dominating customer who makes the product uneconomical if he leaves.
25+ years isn't unheard of, but "in any capacity" absolutely is. There's no foundry on this planet that is continuing to produce you CPUs 25 years from now if your batch size is an order of 50 units.
It would require not only the tooling but also past test runs of all of the verification passes to confirm that the new design doesn't have a flaw.
There are a lot of products that don't change on tech industry timescales (e.g. all those stories of organizations scavenging replacement chips from eBay). It could be really compelling to have the option to use components that are likely be available for 50 years.
But by all means the embedded stuff, motor controllers, instruments and so on should have simple interfaces and either last 50 years or be easily replaced 50 years in the future. This is largely true for industrial stuff. In industrial plants you rarely even have a serial connection to instruments. Instead you will have something like a 4-20mA analogue signal.
I also wouldn't be surprised (and hope) it goes the other way and in 50 years development using FPGAs is as easy banging stuff out in an IDE and making ASICs is as easy compiling and dollars per chip in small quantities.
Modern x86 processors are used in embedded. While there are security concerns if connected to the internet, not all are. These processors don't drive the low level controls, but they do drive the UI - customers want touch screens and other modern UI controls for their equipment. They absolutely do buy equipment expecting it to last for more than 50 years, my company makes a lot of money supplying parts for machines we made in the 1950s - modern machines make us more money, but those old ones are still doing the job for customers who couldn't afford to buy new.
My comment is a reply to the parent but also to the article which I could have clarified. In retrospect I am probably replying to the wrong comment to give my opinion. I think a few CPU part numbers per generation guaranteed to be available for decades is a good idea (and I think it's true already). I also think custom SOCs is a good idea. I just don't think there is feasibility for both custom and long life in the same part.
Then, to reply to you, are you using x86 CPUs in a part of a system that will actually last 50 years? I used to work in automation and perhaps I have a bias based on what I saw in my projects. I was generally paid to automate old machines (oldest was about 60 years old) or upgrade the automation of machines. Sometimes we would keep ancient PLCs running for decades, and sometimes replace them (with a newer PLC that can certainly run for decades). For worn-out mechanical parts we would usually find an old drawing, or reverse engineer an old part and make a new identical one.
But for HMIs, dataloggers and webservers, everyone seemed to be trending towards using industrial products built around x86. These would always be secondary systems and interface to the PLC, but not actually be critical components (well, maybe 1 out of several HMIs is required). But, these tended to be replaced every 5-15 years if they stopped working or a new feature was required, and not maintained with spare parts. It doesn't seem that the manufacturers of these things keep them available for a long time either.
Out of interest, I just looked up the current product line of Beijers HMI panels (I used to mainly use them in my projects), and they seem to be built around Atom, Celeron and iMX6 (great CPU btw) CPUs. Having seen inside the older products, I doubt these have standardized sockets to drop in a new CPU 30 years from now. In fact, the models I used to buy 15 years ago are no longer available and the only option is to buy a newer model and translate the old UI screens to the UI model (either manually or automatically). They do still work with ancient PLCs though.
My thesis is for these, or one of the x86-based "soft PLCs", or in general, for the most part it makes sense to use available commodity parts and keep the product line inexpensive and compatible at the software level rather than select a CPU with 50 year availability. And especially not ask for a custom SoC and then pay for 50 year availability. And not use an off the shelf OS and libraries and hope they work for 50 years. Much better to standardize some interfaces and maintain only those for 50 years.
As a final comment, there are absolutely cases with huge qualification costs or human safety requirements where it makes sense to pay big money to keep using old, proven parts even if they are obsolete, like aerospace or nuclear.