Where we have upgraded networks that include 802.11ac wave 1 APs to 27.6, as expected those APs stay at 26.x. However there appears to be a new firmware 26.9 (similar to the way older MXs go to 14.55 when the network is upgraded to 15.x). However I cannot find any documentation for this 26.9 firmware, anyone seen anything out there?
Generally just using the Organisation/Firmware upgrades page, but that only tells you what they should be on. Hence me only realising 26.9 exists when looking at the Wireless/Access points page which I don't do so often... I'm sure the APIs can help with this though if you have more organisations/networks/devices than we do.