This may be old news to some, but we just first heard about it in this morning's Tom Taylor on Radio-Info e-newsletter -- Casey Kasem's last new countdown will air on Independence Day weekend.
After some Googling around for more info, we discovered the announcement was actually made earlier this month.
Premiere Radio Networks, which syndicates the show, says only the "new" AT10 and AT20 countdowns for the AC format will be affected. The only local affiliate that immediately comes to mind is Lite 98.7 (WLZW) in Utica-Rome.
The CHR countdowns hosted by Ryan Seacrest will continue. And Premiere will continue to supply reruns of Casey's countdowns from the 70s and 80s. Syracuse's WSEN airs the classic 70s "AT40" countdowns on Sundays.