Since the membership count was already answered (no, membership count is based strictly on those living), I'll offer a quick comment on the other half of your question.

From a scriptural sense, the practice is actually based on the concept of modern revelation, where we believe that God has revealed the practice and how it works through modern-day prophets, as was done in the past. The Corinthians scripture ("misinterpretation" is rather open to interpretation) is used simply to point out an instance where it was probably practiced in the churches at the time of Paul.