Mario Kart 8 Deluxe update adds 5 more extra character slots beyond Birdo

It would appear that Nintendo will include six new characters into Mario Kart 8 Deluxe

Mario Kart 8 Deluxe update adds 5 more extra character slots beyond Birdo

Nintendo items with the tag 'deluxe' - NintendoReporters

Mario Kart 8 Deluxe's new character select screen hints at more Booster Pass racers - Gamepur

Mario Kart 8 Deluxe – Booster Course Pass, ST, Doubled Dash!! [WAVE 6 AVAILABLE NOW], Page 137

Mario Kart 8 Deluxe Reveals New Track and New Playable Characters

Wario - Super Mario Wiki, the Mario encyclopedia

Mario Kart 8 Deluxe Wave 4 Update Brings Balance Changes And Five New Character Slots - Gameranx

New Mario Kart 8 Deluxe Update 2.4.0 Available Now; Packs Balance Changes, New Character Stats and More

Source Gaming Presents: Nintendo Kart – Source Gaming