You should be good. If you check the information page about ACMP v8, you can see that ACMA v8 or even v6.4 is valid as the prerequisite, and you can take either the HPE6-A71 (v8.4) or HPE6-A44 (v8) exam.
I found the following explanation:
Updated training & exams for the Mobility certifications.
ACMA and ACMP tracks have been refreshed to include new elements from AOS 8.4. While the certification version stays the same, there are now new training versions and exam IDs:
- For the ACMA V8 certification:
- Implementing Aruba WLAN (IAW) 8.4, Rev. 19.21 (01125755) is replacing Implementing Aruba WLAN (IAW) 8, Rev. 17.21 (01089598)
- HPE6-A70 is replacing HPE6-A42
- For the ACMP V8 certification:
- Scalable WLAN Design and Implementation (SWDI) 8.4, Rev. 19.21 (01125754) is replacing Scalable WLAN Design and Implementation (SWDI) 8, Rev. 17.31 (01089601)
- HPE6-A71 is replacing HPE6-A44
Please note that HPE Press books won’t be updated, but they stay relevant for the new exams preparation.