I don't think I've ever seen Rocket Pass items in the item shop, but maybe at some point they could make a re-release of RP items. The whole concept of the item shop is based on FOMO, feat of missing out, and so is the RP, kinda. If you know Epic will put up RP items in the shop eventually, some people might not spend the credits on the Season Pass and rather wait for them to show up in the shop. Until Epic is running out of new items for the shop, they won't have the need to recycle RP items and they're certainly not going to run out within the next few years.