Heavens, no. If God has not predestined to regenerate a sinner, then you could preach the Gospel to him all day and he will never respond to it.
But if you do not preach, you have denied him even the opportunity to accept or reject the Gospel. Thus, "his blood be on thy hands", for though he would never have taken the offered opportunity (being unregenerate), *you* did not even offer him the opportunity at all, as was your duty!! Hope that is clearer.
I hope I have somehow misunderstood you here.
I think you have. I speak not of some class of persons who would be saved if only they were preached the Gospel, but rather of Preachers who "share their guilt" in an ethical sense, for never having bothered to offer them the opportunity for salvation in the first place. They would reject, sure, but the Preacher would at least have done his duty.