Only a few? I've heard a lot, and I've seen it stated explicitly in service bulletins and heard it stated explicitly by pastors in giving an open invitation.
I do think, however, that we probably should draw a distinction between "communing unbaptized persons who present themselves to be communed" (which a pastor may or may not even know) and "explicitly or implicitly inviting the unbaptized to receive the sacrament."
In any event, you are right that this needs to be watched carefully. I believe there will be a strong push to move this question into the murky area of "bound conscience," letting congregations and pastors do whatever the heck they please.