Mojang Studios has announced that it will be merging PC Minecraft users' Mojang accounts with Microsoft ones early next year, meaning you'll need an Microsoft account to access the game's Java Edition going forward.
In a post on the Minecraft website, the studio announced the move would be to allow users to utilise features such as 2 factor authentication, have all their Minecraft games including Minecraft Dungeons on the same account, and also offer improved parental controls as well as chat and invitation blocking.
The studio also moved to reassure players that upon migration, they'll still be able to create and use mods and skins as well as keep their existing ones as well as getting to keep their Minecraft username and won't be locked into the Minecraft Marketplace as is the case with the Bedrock Edition. To encourage players to move, they'll also be offering a free cape to any user that moves their account across.
New users will have to login with a Microsoft account to use the Java Edition as soon as this Fall, while existing users will be moved across in "early 2021." Mojang say that this will happen in stages, with users recieving an email with instructions on how to perform the move when it's their time to undertake it.
You can check out a full FAQ on the move on the Minecraft Support website, and check out a video on the announcement for Minecraft on PC below.