Kris, since you asked, "What is the newest...", I'll chime in and say that the 76xx series would be the 'newest' series of APs that are compatible with the RFS4000. I think you'll also find that they're less expensive than the 75xx APs...but I'd rather stay away from pricing as part of discussions here on the Hub.
Like the AP7522 and AP7532, there is also a AP7622 and AP7632. (All of these are wave-2 .11ac APs though)
But, the AP7622 is a little bit different beast. Explained in a minute.
If pricing is the ultimate decider here, go with the AP7622, but understand EXACTLY what you're dealing with. It's a *single* radio, dual-band AP. It's 'sharing' streams, so if you want to use both 2.4 and 5GHz simultaneously, each radio will be 1x1:1. If you only use either 2.4 or 5GHz, then it will be the full 2x2:2. The goal of this AP is to keep cost down.
(The 7632 is a full dual radio, 2x2:2 AP)
If possible, go with the AP7632 for better potential performance.
If pricing takes a back seat, and you need the best possible throughput, then go for the AP7532, then followed by the AP7522 or AP7632.
7532 is a dual radio 3x3:3 AP
7522 is a dual radio 2x2:2 AP
7632 is a dual radio 2x2:2 AP (with BLE radio)
7622 is a single radio but dual band capable AP (single band 2x2:2, or 1x1:1 dual band) with BLE radio)
The 76xx series will have a longer support life though since they're newer.
So to break it down by performance, from top to bottom it would be:
1) AP7532
2) AP7522/AP7632 (Both are dual-radio 2x2:2 - AP7632 has a BLE radio also...and is newer)
3) AP7622
If you want an AP that is going to have the longest support though, go with the 76xx series.