"Data is easy and inexpensive for miners to hold and proces…

I agree with craig. Unless the data is illegal, I don't think miners will prune it. And if they do, I think they will only prune the largest files. There is value in holding that data in 2 ways and the cost is negligible for text & images.

@100 on the topic of purnability of data and how to ensure with more certainty your data is preserved after the genesis update. Beware, long but worthy article.

https://blog.bsv.sh/the-prunability-and-non-permanency-of-your-data-the-case-of-op_return/