Using an 11 Pro Max here to replace a damaged XS Max. I'd like to see a larger mAh, but with refinements to 2021's A15 SOC, and using Qualcomm's successor to the X55 used in the current 12, we might not need a larger capacity battery. Qualcomm's X60 is built on a 5nm process unlike the 7nm process the current X55 is being built on. This alone should result it improved power efficiency. Combine that with an even more power efficient Apple A15, and Apple might leave the battery capacity alone, although it would be nice to see that increased.
I'd personally like to see the following
120Hz (spoiled by my iPad Pro)
USB-C (wishful thinking, extremely unlikely.. they will probably remove the lightning connector all together)
Better camera for super close ups.
I only think 120Hz is likely. The rest is wishful thinking.