_Everyone_ will be completely forgotten. I think the obsession with "legacy" is a fools errand. Making a positive impact yo those around you, big or small, _for the sake of it_ is a more reasonable approach, IMO.
Even the most successful person will be forgotten[1] within a few generations.
1. Forgotten as a person, but possibly reduced to a name and a title without knowing eye color or personality.
The jury is still out, but I wouldn't bet against entropy. Cloud companies do not yet have a clear guidance on what to do with data belonging to deceased users, but if that data is not profitable, it'll likely be deleted[1]. Phones and NAS devices will end up in the attic or landfill: sure programmer-archeologists of the future may encounter some with partially recoverable files, but most of the present day data will be lost.
1. I missed a payment to a SaaS provider by a week (I was traveling) and irrevocably lost data. When the payments stop due to infirmity or death, the data will be deleted.