I think he was referring to Unlimited air racing in the USA - most of the racers are either Merlin or Griffon powered Mustangs, or Sea Furies re-engined with R-3350s. Still a couple of Bearcats going as well, and some Yaks. There are three or four specialist engine shops in the US "churning" out rebuilt race-tuned Merlins for the speed freaks.
The only potential Napier Sabre powered flyer I can think of is Kermit Weeks' Tempest currently undergoing rebuild with PPS at Booker. Whether it actually will fly is doubtful.