Once again, it’s pledge time on PBS, when they bring out all their special shows, including reunions of soul and doo-wop singers from the ’50s, ’60s, and ’70s. Which means that when I’m in my 60s, I’m looking forward to a pledge special of hip-hop and R&B. Picture it now: a PBS special featuring Ice T, Ludacris, Salt-N-Pepa, 50 Cent, Destiny’s Child (“for the first time in 30 years”), Snoop Dog, Missy Elliott, … After all, if the Smithsonian can exhibit hip-hop, surely PBS can.