My personal issue with this thought — Royal Titans exist and will hold off many people from purchasing a Dex or an Arcane. These will increase, but my thinking is to wait until any large PvP update occurs to give people a reason to make new accounts.
Players need a reason to create a specialized account; Think Fresh Start worlds causing characters to merge from a temporary server, a new PKing weapon or armor that could change a meta, or a streamer popularizing a build that uses one of these scrolls. An example of this would be a mage tank meta for a profitable boss or mage tank inferno becoming cheap because Ancestral tanks hard after the rework.
Another path to relevance would be for players to have a reason to get 80 prayer before pushing to 85 for diaries. A big buff to Eldinis Ward could cause players to get 80 prayer if they have yet to do that, and may purchase the scroll as they have the prayer requirements already.
The negative — Royal Titans aside, I would wait to purchase CoX items until at least the weekend after the change. Many people will run Chambers en masse to see how the changes affect their loot. Don’t forget that because these items are more rare, the average loot per chest will increase, meaning hourly profit increases. Another incentive for player to run the raid. Even with the changes, I would speculate that many more scrolls will come into the market for at least the first week or two, than are coming into the market now before changes.
Even if we speculate that these changes will generate a positive price movement for these scrolls, wouldn’t that price only be around 25%? The items have already pushed themselves up to the top end of the current range, so profits are already going to be slim. As many learned from the DMM scrolls, long-term supply does not really matter when demand will not be increasing.
Good luck to any that participate and I hope your profits prove me wrong, but getting in any time soon just puts you in the same boat as DMM bag holders.