Assuming your statement is correct, “Hemp paper is good for 200+ years, so is much better for valuable books”, it will, as the Sharks say, likely remain a niche market.
Unlikely the paper industry is concerned, if for no other reason the shear volume. Pound for pound, all the legal hemp grown in the US probably will not surpass one truckload of pulpwood trees.
Except that time and expense are factors. Figure on two hemp crops a year, compared to say 20 years for tree maturity. Plus logging and transport is quite expensive, but much of the processing for hemp could be done in the harvester before it even leaves the field.
Importantly, the paper industry is already mostly tooled to handle hemp pulp, which needs fewer steps in the process.
You can probably calculate that with legalization, hemp agriculture would have a production boom in the amount of acreage; so the first bottleneck would be in processing it.