A) You keep your old laptop and continue to run macOS for as long as possible
B) You're shopping for a new laptop and don't buy Apple, then run Linux
If you keep your old hardware why run Linux on it? I've been looking at who else is out there are making decent laptops that run Linux well (open to suggestions, especially if they have more than 16GB RAM), as I have a feeling my 2015 Retina will be my last MBP.
The hard part for me is that I've gotten used to a certain look and feel with the MBP. That nice solid, rigid body, and the display hinge that just stays. When I pick up a ThinkPad and it creaks and flexes when I open the display or casually pick it up by the corner it makes my skin crawl.