One D&D's Affect on Purchased Books

Hello everyone. I am concerned that, after having purchased the Player's Handbook , Xanathar's Guide , Tasha's Cauldron , Monsters of the Multiverse and the Fizban's Treasury books on Roll20, that when One D&D releases in 2024 the compendium will change to reflect the One D&D release. I am hoping that the 5e books stay as they are on Roll20, but that might not be the case and I have no idea if One D&D is going to be treated as a different set of rules or if I will have a Legacy version of the books to look through. I have not found any info in the Roll20 forums OR on DnDbeyond's forums about any kind of changes to the compendium, and would be most appreciative if anyone could share their insight on the matter.

I don't think you will have this issue. One D&D is essentially 6e or even 5.5e. It is a completely new edition that just happens to be backwards compatible in that you can run 5e modules and the like with the new rules. I believe this was confirmed in one of the Jeremy Crawford interviews that have been cropping up on YouTube regarding One D&D as well.

My feeling is that Roll20 has no idea yet, not being privy to boardroom discussions by WotC. When Monsters of the Multiverse came out, it supplanted several books: Volo's Guide to Monsters and, Mordenkainen's Tome of Foes were delisted from the D&D catalog. Neither is for sale anymore, but if you purchased them on Roll20 before the event, they are still in your purchases. My personal, completely unsupported, prediction is that folks will retain their purchases unaltered if there are substantial changes (it would actually be more work to convert an existing compendium source than to add a new one). I'm guessing they will just be more compendium sources you can turn off and on, or if the changes are great enough, they will be the basis for a new compendium.

Did some quick digging. In the recent YouTube video "One D&D Survey Results and The Future of One D&D" on the Dungeons & Dragons channel at 11:23 they talk specifically about Fizbain's and how that can fit alongside of the new edition. Later in that same video they discuss how they are using 5e as a starting point for this new edition. I actually highly recommend watching the videos that have been posted as they're actually quite informative.