It's the fan bracket that's changing for V4:I'm also interested in that new side panel you mentioned might be coming with the v4. Do you plan on having that has an extra as well?
It's mainly to allow us to include a magnetic filter with the case. But it also has an extra 2mm of travel in the fan mounts, which is potentially useful as it allows a 140mm fan with 120mm mounts to be installed alongside a regular 120mm fan. This was sort of possible with the old bracket, but it wasn't quite enough room to do it properly and not induce some flex in the bracket.
We are ordering some extra of the V4 brackets+filter for V1-V3 owners, if you're interested in it.