My slight concern with the M5 MBP is that the M6 MBP is going to change the shape of the display. Using the iPhone SE is kind of annoying with the shorter relative height of its display and the software designed around a taller display. If Apple removes the notch with the M6, there might be some display issues on notched laptops with software designed for no-notch laptops.
I'm also using a 2012 MBP and am considering upgrading to the M5 MBP. Redesigns are scary because that's a good opportunity for them to mess things up (e.g. by designing display cables that are too short) or remove loved features (e.g. MagSafe, HDMI, SD Card slot, Headphone jack).