Additional Rune Pages? How to spend IP?

So rune changes are coming. The announcement said you get full refund for any IP on runes purchased this season. It also said you can use the additional rune pages purchased in the new system.

???Are pages in the new system free? Why did it mention you can use the additional pages purchased. What is the best way to spend my IP before this new system. I thought I should just buy a rune page since it says it will move over to the new system.... but if they are free anyways there is no reason for me to buy pages. I want to spend my IP because they give it back later.