I think defining what constitutes scale by the comments I have read so far is a matter that's best characterized as beauty is in the eyes of the beholder and that seems to fit the wiggle room there is for what is, in reality, is a definition that is not set in stone so one could say: "this is scale and that is not scale.. I think HO and it's influences has permeated O scale that led to Hi-rail and now.."scale."
For the buyer who has bought this philosophy of modelling, I think will find that satisfying themselves in reaching this high bar will result in more parsing over new product..as well as more modifications to out of the box models...and increased cost.
I think some of the concern expressed here is that those who find this form not particularly attractive sense that they will be dragged into this if the manufacturer's follow their lead of scale realism dominating the O hobby...In other words if what constitutes O significantly changes.
I suspect it won't....if there was a really big desire to go this route, two rail O scale should have taken off like rocket. It hasn't. At the same time from what I see everywhere I read this or that, there is a "sameness" to what is published..less variety of modeling styles..you could make the argument that what is published is an influence I suppose.
Its ( scale three rail ) a nominal sub grouping of interest that has it's own merits but frankly I do not see this as a big trend..it has its own limits.
Take traction modeling for example..if you want a large variety of product, there is O scale realism as two rail O complete with high cost, brass models, a lot of scratch building, detail parts to be added..on and on. Again, this is a nominally small segment of the hobby. In scale traction,there are few if any alternatives. I just don't see "scale" really taking off to this extent...where choices become shrunken to the point of exasperation. As for me, I never saw a model train that I didn't like in some manner....