No. Wing controller operating on newer Wing 7.x release can not adopt Wing Access Points on 5.x release.
Note : With the release of WiNG WiNG 184.108.40.206-015R it Added legacy AP support for the following APS:
and are now fully supported on WiNG 7.2.1 release with the same feature set as in WiNG 5.9.6
Please see release notes WiNG 220.127.116.11-015R Release Notes