Apple sent out invites yesterday for a pre-Halloween Mac announcement. The MacBook Pro is believed most likely to get updated at the event, but honestly iMac is likely not out of the question or maybe even MacBook Air. So to avoid buyer’s remorse, maybe wait until after October 30th to buy a new machine.
Utilization doesn’t matter, unused RAM is wasted RAM and macOS will use all available memory to give the user a snappier performance. Only consider more RAM IF you see red memory pressure graph or experience any hickups and slowdowns in your workflow.