I have taken the plunge and replaced my Pi3 with the Pi 4.
All seems to work well with HEQ5, 294MC, 224MC and Pegasus PPB.

One question I have is should the Update button in the StallaMate dashboard work?
Mine runs the percentage usual goes to about 3% then I get a message saying the update was successful but the update icon remains red with a little red exclamation mark next to it.