Well, yes, if you could scan the o-neg at 4K, you'd almost definitely get better detail than the official BD even if you then downscaled to 1080p; the problem is that the best source that is likely ever to be available to us is a theatrical 35mm print, which most likely doesn't even resolve 1080 lines to begin with - the best you can hope for is to get about the same level of resolution as the official BDs (and that would be pretty amazing to be honest) with hopefully better balance and more shadow and brightness detail, so doing this at 4K seems a bit pointless to me, unless you were doing something like Mike V. and combining detail from multiple prints.