As far as I have seen, all Gen4s use the same menus etc. So even my original Gen4 Disc (v14) is no different to older ones, apart from the newer Maps.
An update for Keenwood's internal Firmware hasn't come up anywhere afaik. That would be nice, but I guess they would only release an update to fix issues, and there aren't really any. Newer features or less grainy maps came with newer & larger displays like the Gen5's, so no real reason for them to spend time to upgrade the Gen4 FW, although that would be awesome if they did. We're probably limited by the screen's physical resolution in the end. I haven't seen Gen6 screens, but they're probably an improvement in size & resolution again over then Gen5. But I doubt FW is interchangeable between any of them.
If someone were to pay the ~$300 for a genuine Subaru Map disc, they'd definitely have the combined map and software
. I assume Subaru still sell current discs for Gen4s, but maybe Whereis discs are cheaper. So for whatever reason, the torrents all seem to be non Subaru map update discs.
I'd gladly go for a group buy for a new genuine Subaru Disc, if we had eg 10 people
.
Combining the software and maps should be possible in theory. But the discs do not just contain a simple 'Map' and 'Software' folder. I'd pay someone who is a software programmer for eg Subaru to tell us what files the Nav looks for for the software, and which ones are the maps. That would allow us to always make combined discs that work even after a battery reset. But I bet no one like that is out there for hire. BBB has asked this question before on here, and there was unfortunately never even a hint of info for what's required to do that.