Just read a few articles about the launch - seems like they’re moving their account system to Epic and you’ll have to link your current Dauntless account with an Epic account and that’ll then be your login as they’re moving the PC version to the Epic Store (also means you’ll need to redownload). Whether that then means you can log into your Epic account on the xBox and carry on seamlessly I’m not sure. But they have said PC and xBox cross play will be enabled, so there should be a lot of people playing if its popular. PS4 won’t be at first due to the usual Sony red tape BS.
Edit : Ah - found a post from their community manager - they’ll have cross-progression working at launch, so it doesn’t matter which system you use, it’ll all count - you just won’t be able to do a hunt with someone on the PS4 if you’re on PC/xBox and vice versa. Also, the premium currency earned in game will work cross platform but any purchased premium currency has to be spent on the platform it was purchased on.