Years ago, Diva Past (whose career, by that point, was really done) canceled a prima donna gig at a major American opera house. Diva Present won overnight stardom when she substituted. Now, years later, Diva Present has booked a return to both venue and role of her triumph. At the moment, though, her schedule is extremely nip and tuck. And so the doubting opera company is about to send on … Diva Future. It’s the circle … the circle …. of divas!