If you want the new versions of the books the yes, you will need to purchase them. If you are happy with the current books then you will be able to continue using them. Heck, even if you do purchase the new books you should still be able to use the current ones too.
curious on some things like, for instance, if my hundreds of dollars of DND beyond purchased content is about to be obsolete?
I have been out of the loop for about a year. Will the new DM Guide, Player Guide, Monster Guide, etc. all have to be re-purchased ?
If you want the new versions of the books the yes, you will need to purchase them. If you are happy with the current books then you will be able to continue using them. Heck, even if you do purchase the new books you should still be able to use the current ones too.
For more info regarding 1DD, you can check out the Unearthed Arcana forum: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/unearthed-arcana).
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