Yeah, I think my Mac Pro 3,1 will be fine, and even without Mojave, I think we’re getting High Sierra security updates for like another three years anyway, so by that point we ought to have the new modular Mac Pro, and I’ll have to do a cost/benefit analysis of what the next step might be from there, one way or another. But it seems like it will work out.
Come 2021 or 2022, either I’ll buy a new Mac Pro, buy a decently priced higher specced Trash Can, or gut the 3,1 for the case and go the Hackintosh route. I know Apple is really trying to get to the point where their chips are proprietary (return to the PPC era, kinda!), but despite a lot of complaints in this and other threads, Apple does have decently long support. So I wouldn’t expect an intel based system built in a year or two to not be supported by quite a few subsequent macOS iterations. I mean my main computer is a 10 year old computer and I guess High Sierra has finally settled down on .4 (I still need to install .5, probably do that today, so cross fingers), and I’m experiencing no issues.
Now, when it comes to MacBooks, that’s a whole other issue. I sold my 2012 MBP 13" and I’m on a 2008 MacBook White 2.4GHz Core 2 Duo as my school/work device running Linux Mint. I’m just completely lost as to what MacBook/MacBook Pro device to pick up. Should it be used, should it be new, what kind of upgradeability will it have if any, if it’s older and used, how long before I lose access to something like even Mojave, let alone future OS releases… I just don’t know.