Earlier quoted context omitted.
Of course, what you do is publish plenty of different hashes on the block chain(s) of your choice. Then you can later reveal what you feel like.
Don't really have to involve blockchain here (yet again), publishing on a website and letting Internet Archive archive it is good enough. Or even posting it on Twitter/HN/$social-media-with-edit-limit
(/sarc; I love seeing how far one can go down the opsec paranoia rabbit hole if one really tries. ;) ).