"Definitely on Xbox One X, 60FPS. On Xbox One, we’re not sure. We may have to limit it at 30FPS, maybe, but the last time I saw it, it was running at about 30 to 40. We’re still constantly improving it so, you know, the aim is to get to 60. That’s why we’re doing Game Preview, because I think the great thing about console is it’s a locked hardware system, so we can do really specific tweaks that tune it for those systems.
I have great faith that we’ll get there. The great thing about Battlegrounds is that it’s not…unlike the more high paced shooters, frame rate isn’t that important. Yes, it is important, but it’s not as important for us as it is in a twitch shooter. So we’re aiming for 60; not sure if we’ll get there, but that is our aim."
Source: https://wccftech.com/playerunknown-xbox-gaming-60fps-xb1x/
Honestly didn't expect the game to be 60fps on XB1X so that's great news. Hopefully the XB1 and XB1S can reach 60FPS sometime during game preview.