Due to the transfer between companies, players will need to expressly consent to allow their game data to be transferred over. The announcement post contains instructions how to do just that. Also, Sword 2 players won't be able to transfer their GamersFirst store currency, so spending it now is highly recommended.
There are a lot of details to go over, so if this affects you, be sure to read the whole post very carefully.
[Thanks to William for the tip!]