We made a post over a year ago in October when Mojang Studios announced that all Minecraft: JAVA Edition Mojang accounts would eventually need to migrate to a Microsoft Account to continue playing. Earlier today Mojang released an article noting that starting on March 10th you will need to have a Microsoft Account to continue playing Minecraft: JAVA Edition.
If you don't migrate your account by then don't worry! Your account is not lost. You can still migrate your account to a Microsoft Account but you will not get the previously mentioned cape. If you would like to read more information I've included a link to the FAQ for you to review.