Is PRL Too Large to Have an ‘‘Impact’’?

Recently there was published a PRL Editorial with such a title. The main message is that only a small fraction of Letters are really highly cited - if one publishes them separately, they will have an impact factor of about 20, while PRL's number is about 7. So, this might be a good idea to reject more papers and accept only revolutionary contributions. However, the problem is that nobody can actually predict how many times a given article will be cited in a few years...