I love the 2.0, and id rather see some updated panels rather than a 3.0. But here are my thoughts.
*Motherboard rear access - I know some people will complain that is spoils the clean sides, but it would make hardware substitutions so much easier. Plus if I need to redo the thermal paste or the like I dont have to empty the entire case.
*Aluminium case - Same design, but in aluminium, the sentry can be quite weighty when fully loaded, Plus I can imagine benefits to cooling, as there will be less hot spots (certain parts of my case get to "too hot to touch" levels when gaming for extended periods
* Cooling improvements for SSDs and NVME's - I havent had any issues so far but I worry about the longevity of the NVME on the back of the motherboard, must be scorched 24/7
* Improved segregation of GPU/CPU compartments - I mentioned this before, could either be some cable management style grommets, or a plastic "passthrough" where PSU cables connect to it, then on the other side (gpu compartment) plug in a seperate power cable to connect gpu to passthrough. Im for this not just for tidyness, but hopefully would improve thermal performance if no GPU hot air can get to CPU compartment, only through conduction via case.