Generally speaking, I do think that PC based PLCs are coming more and more.
But I do expect that product life cycles will be shorter, and reliability will be less.
I'd argue that there really isn't a fundamental difference between a PLC, PC, Tablet, Phone, etc anymore. Microprocessors and memory have become so cheap, the real difference are in the software and intended application.
I dont agree with that. In PLCs there is a difference in both hardware design and testing that emphasize ruggedness (can take a beating mechanically and electrically), reliability (wont last only 2-3 years like consumer electronics do these days), and simplicity (not being dependent on for example USB drivers for the devices used).
[..] it appears that trend is going away as well since, most things are done in software now [..]
True, but even for software the big PLC brands are still much more conservative and perform more testing than consumer/office brand products. In particular for the devices that control something.
[..] and hardware component availability life cycles are so short.
The availability of components in current PLC designs cannot expected to last 20+ years like they used to. But for current PLC designs the availability of components must still be much longer than consumer/office grade equipment.
The other way to handle the obsolescence of parts is to always have a migration path to a newer version of the same hardware. The big PLC brands will not leave their customers high and dry when the parts are unavailable.
@jdbrandt. I think that what you describe is that people that are used to work with control systems and PLCs have a totally different mindset than people that work with PCs. We are used to think about things like doing proper backups and documentation because of hard-learned experiences. When a non-PLC guy (manager) asks another non-PLC guy (intern) to make a control system, it is a disaster going to happen.
edit: I just reread my own post and realize that my words sounds denigrating towards PC programmers. Of course PC programmers also document things, but the mindset is different. The PC programmers i know of think for example that it is vital that all programs are stored on the same Git server, and the latest updates are always automatically pushed to the endusers.