AireOS:The new version of the exam is based on AireOS 8.0 (previous version, v2, was based on 7.0). It is therefore fair game to expect to see "some of the new stuff" that appeared between 7.0 and 8.0, such as mDNS, IPv6 (for the infrastructure, IPv6 for clients was already in v2), 802.11ac, SSO, 802.11k/v/u/w/r, AVC, device Profiling, onboarding, RX_SOP, RF Profiling, but also all the enhancements that came into existing features, such as RADIUS DNS, QoS profiling from ISE (yes, ISE replaces ACS), wIPS, DNS-based ACLS, L2 ACLs, Min/Max power for TPC, and tons of changes on the Flex APs (local PEAP or TLS for example), not to mention new features on the MSE like Visitor Connect...
Okay, let's cut it short. It is not one of these updates where you think "I just need to brush up one one or two items, and I'll be good to go". You probably want to do a clean study of the entire WLC config guide 8.0. At the same time, the update from v1.0 to v2.0 also displayed a daunting list of changes, which is to be expected when an exam jumps across two major releases. Even if the list above looked scary to you, it is very likely that you have heard of, or worked with, quite a few of the items in that list (unless your boss really thinks that 7.0 is the best code on earth). And if you have not heard of some of the items in the list, it is likely that they are not fundamental (doesn't mean that you won't get them in the lab, but they are likely not to be the core of your exam). The logic of any exam is always: make sure that the candidate knows the core of the body of knowledge (for example, it would be funny if the CCIE R&S exam did not test routing or VLANs). Once this is taken care of, the expert exam tends to test tinier items. The less items on that 'non-core' list, the more in depth you can expect tests on these "tinier items" to be. Similarly, a longer list means that you are unlikely to be tested very deeply on many of these tinier items. Why not? Because despite Non Disclosure Agreements that people sign when taking the exam, people still talk, and it would not take long before forums would display "they only test items A and B". So, a longer list means that you are likely to get more items (and different items in each exam set). As the exam duration is still the same, each item is tested less in depth. It is still likely to be an expert level, but there is "expert" and "crazy expert". More items pushes the bar from "crazy" to just "expert", knowing your stuff well should be enough.
IOS-XE:That's another scarecrow. As Converged Access is in the lab, you are likely to get 3650/3850 Switches and/or 5760s (maybe, maybe not, but likely). Are you expected to be a guru on these platforms? My bet is "probably not". As these beasts are on the blueprint, you need to know how to configure them for the classic functions that a wireless guy can expect from these boxes (WLAN, MC, MA, PoP, PoA, etc). However, these devices embark the IOS, and can do much, much more than wireless. A wireless guy is of course expected to know basic routing, but it is very unlikely that you may need to configure insane Wired-only functions. If you are comfortable running basic configurations in the GUI, you probably know most of what you need to know to survive this part. Add knowledge of what CLI configuration is done when you configure this or that in the GUI (in other words, survive the CLI), and you should be very close to where you need to be to enjoy the CA section in the exam. A common misconception about this version of the exam is that you need IOS-XE as deep as AireOS.
MSE/ISE/PI:MSE is in the exam, with new functions. If you get a chance to read on what you can configure, you will soon discover that, just like in v2.0, the scope of what can be asked is limited. Rent and MSE for a day or 2, and you should know enough to be comfortable with any question. The same goes for PI. I often ask myself: what can they ask in PI that you could not find with a few clicks? Learning the interface is not hard... and all you need to know is the interface (there are very few features that you will find only in PI, and not in the WLC, that you would care about as a Wireless engineer).
ISE is just like ACS: scary because it is an entire world. Here again (and just like ACS), you are the wireless guy, so there should not be any feature that is so deep that you would need an ISE expert to help you. Knowing how to create standard policies is what ISE is about in the Wireless IE.