Earlier quoted context omitted.
We invade the privacy of people from a few hundred years ago all the time and it's considered fine. Do you think there will be a breakthrough in encryprion breaking soon enough for it to matter?
Assuming this will take a few hundred years. Browsers have to frequently deprecate cryptosystems that have become insecure. That's not possible with data frozen inside the blockchain. Also, we're at a point where quantom computers are just starting to become practically usable. So yes, I think the point of a "cryptographic breakthrough" that will crack some configurations is quite likely.
And if you're not encrypting data with AES (or one of a handful of other algorithms), then you should be worried _now_.