I recall watching a documentary (on Curiosity Stream maybe? I'm no longer subscribed) on data storage longevity. It covered DNA storage, which I think this PBS video w/ transcript provides more recent coverage of its developments. As well as holographic storage, which I could only find the Wikipedia page for.
As for which one I think might be the future, it's tough to say. Tape is pretty good and cheap but slow for offline storage. Archival media will probably end up all being offline storage, although I could see a case for holographic/optical storage being near line. Future online storage will probably remain a tough pickle: cheap, plentiful, fast; select at most two, maybe.