Jabawocky and Biggles in Oz;
As one can't be half pregnant, nor should there be any doubt about what is IFR and what is VFR. Much has been written about this.
If RPT or somebody TCAS equiped or not,descends into a CTAF they are either visual or doing a non precision IFR approach at minimums. In either case somebody should be looking out the window in addition to ATC or TCAS information. If it is IFR to minimums, VFR traffic "should" be on the ground, BUT in case of some Croppie or Drifter beetling around the CTAF, they "should" alert all via wireless communication.
You can't legislate against stupidity, so it beholds all to look out the window in addition to radio, ATC information and TCAS information.
I think it's called the triple condom thingy.
BTW and not wanting to draw bow strings further, has it occurred to the VFR pilots out there that IFR traffic need an alternate and if some outage occurs with new fangled technology, the alternate has to be one of the aids that the salesmen are talking about decomissioning.
No, sorry, lets not go there.