Heads-up for Fortnite account going from PS4 to Switch (not sure about Xbox). You can't so you'll be forced to either buy another battle pass or just not play it on switch.
Fortnite - Season 6 Battle Pass: Now with Pets! | PS4 - YouTube
UPDATE: Fortnite Season 3 Battle Pass start date, NEW Battle Royale rewards news | Gaming | Entertainment | Express.co.uk