I assume he is... So is Don Kellner... If they'd stopped, I'm sure it'd be newsworthy.
Hundreds of jumpers stop every year. Unless they themselves made a big deal of it, why do you think Bill and Don's retirement would be so newsworthy?
Don't they have more jumps than anyone else in America?
If football player Brett Favre retired, that would be news. If golfer Tiger Woods retired, that would be news. Likewise with Bill or Don, at least among the skydiving community.