The RFS series controllers have limited amount of flash available and the following are the pre-oaded AP images when upgrading an RFS wireless controller (example from RFS4000 v5.8.6.7):
RFS4K-WAN#sh device-upgrade ver
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CONTROLLER DEVICE-TYPE VERSION
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RFS4K-WAN ap621 5.8.6.7-002R
RFS4K-WAN ap622 5.8.6.7-002R
RFS4K-WAN ap650 5.8.6.7-002R
RFS4K-WAN ap6511 none
RFS4K-WAN ap6521 5.8.6.7-002R
RFS4K-WAN ap6522 5.8.6.7-002R
RFS4K-WAN ap6532 5.8.6.7-002R
RFS4K-WAN ap6562 5.8.6.7-002R
RFS4K-WAN ap71xx none
RFS4K-WAN ap7502 none
RFS4K-WAN ap7522 none
RFS4K-WAN ap7532 none
RFS4K-WAN ap7562 none
RFS4K-WAN ap81xx none
RFS4K-WAN ap82xx none
RFS4K-WAN ap8432 none
RFS4K-WAN ap8533 none
All other AP images would need to be uploaded to the RFS controller and typically no more than 2 to 3 additional images can be uploaded to the controller.
As for the RFS7000 comments, the RFS7000 has been EOS for a couple of years now, with plenty of time for customers to refresh. The code is the same across each platform, but the hardware is not.
For the time being, with 802.11r disabled and broadcast key rotation is disabled (both disabled by default on all WiNG 5 platforms), you should be fine, but would start looking to refresh your RFS controllers with newer models.