I currently have a single IAP controller that is supporting the following models and will be upgrading to the equivalent 500 series as shown below. I'm struggling to find a way to run both 200 series with the newer 500 series. My problem is trying to find the sweet spot where both the newer 575/577s are supported with the 200 series. Looking at the 8.6.x, 8.7.x release notes, it looks like I'm good with 200 series on the 8.6.x, but 575/577s are supported. When I review the 8.7.x release notes, it looks like I'm good with the 575/577s but a lot of the 200 series drop off the list. Then I found a link below that shows ArubaOS 8.8 supports all the models but this seems to connected with the controller, not instant - but isn't the controller and instantos one in the same now?
204 --being replaced by 504
205 --being replaced by 505
205H --being replaced by 505H
275 --being replaced by 575
277 --being replaced by 577
325 --being replaced by 525
https://www.arubanetworks.com/techdocs/ArubaOS/Consolidated_8.x_RN/Content/8.8/overview-880x.htm#SupportedPlatforms