The is_sidepath=* proposal looks like a good replacement for name=* on sidewalks. However, it's still at the RFC stage and as far as I know the only routing software which currently uses it is cycle.travel, which isn't a pedestrian router.

Before the proposal goes to a vote, could I suggest adding is_sidepath:of:name=* while retaining name=* for now. This is the approach I will take for some of the sidewalks I've added in the near future.

The justification in the wiki for asserting that name=* should not be used on a footway=sidewalk is from your own recent edit. Perhaps this should be discussed on OSM Community first - you may well get a consensus agreeing with you.

If the proposal moves to a vote and is accepted, I feel that would be the time to discuss the timescale (if any) to migrate tagging from name=* to is_sidepath:of:name=*