Yeah, it wouldn't be surprising. But good for the game. It already sold well, but can sell even better.
As for online play for f2p games, apparently you don't need a PS Plus subscription to play Fortnite with friends on PS4, but you do on Xbox One: https://metro.co.uk/2018/04/10/need-ps-plus-xbox-live-gold-play-fortnite-7455044/
Yeah f2p is free on PS4. I guess the announcement will accompany Fortnite switch announcement. Otherwise maybe assume it's not.