You can safely assume that there will be SSD upgrade units available in the future but you can also safely assume that their prices will never be attractive.
Still, you can equip the laptop today with up to 16GB RAM and 1TB SSD and I would think that sufficient for most non-media-editing use cases even 5 years out.
From experience, I would say that Macs have a lot of "fringe benefits" as a commercial computer.
-The software is all incredibly easy to service. You could teach a middle school aged child to perform a clean wipe, reinstall Mac OS, restore from a Time Machine backup, and make sure that everything is updated, in about 15 minutes.
-Hundreds of thousands or millions of people have the same EXACT mac configuration as whatever mac you have, and a greater proportion of those users are digital professionals or other relatively sophisticated computer users, so if you are ever having any problem with a mac, you can google it and find 100 web pages describing the exact same problem on the exact same hardware with the exact same software and how to fix it. PCs come out with all sorts of changes every few months based on what parts are available cheapest to the manufacturer, and there are more customization options, so its harder to find support that's as accurate and relevant.
-Most younger employees prefer them
-enclosures are more durable and take wear better than the plastic enclosures on other brands
-there is a unique serial number printed on the outside of every Mac that is much more resilient than the decals with similar info on PCs
-Only 2 different formats of power adapter to power any mac laptop of the past ~8 years
-standard MiniDP/Thunderbolt>X video adapters work for every mac from the last ~6 years
-Apple TV screen sharing is the most reliable way to get your desktop up on a TV or projector without plugging in
-Time Machine is reliable and more user-friendly than any backup solution available on Windows (and user-friendliness is a big factor in whether your employees will actually perform backups)
-Mac OS whole disk encryption and Time Machine backup encryption are more reliable and user friendly than any comparable solution available on Windows
My company used to use Dells and it was a nightmare whenever I had to reformat one. I could use the "Dell Service Tag" to look up what drivers applied to that model of laptop but it wasn't down to the specific parts in my specific machine, it was only down to the drivers for all parts available for the model, so I had to figure out what components were actually inside the computer. And then I had to manually install the drivers one at a time. In a specific order lest I have to start over. With Macs I just create a USB bootable install drive and I'm 99% done.
