When Radio Hall of Famer John Records Landecker fills in next week for morning host Bob Sirott on WGN 720-AM, there may be a lot riding on it for both Landecker and the Nexstar Media Group news/talk station. If all goes well, insiders said, Landecker could be in line to host Monday through Friday evenings and serve as Sirott’s regular substitute in mornings, starting this fall. The two Chicago radio legends have been friends since they worked together at WLS 890-AM during its Top 40 heyday in the 1970s. “Listeners are going to discover that John’s middle name truly is ‘talk,’” Sirott joked. Meanwhile, one familiar voice we won’t be hearing on WGN is Garry Meier. Management sources confirmed there were talks with Meier about replacing afternoon host Roe Conn (whose contract is up at year’s end). But serious negotiations never got off the ground, and WGN bosses quietly dropped the idea.