I skipped 5. Have 4 Black.
The reason for skipping 5 was mostly because it wasn't much of an upgrade but a chock full of bloat.
I shoot in 4K, but mostly in 1440p60. I love super high resolution with high fps for a 'live' feel(not 'cinematic' 24 fps blurry mess). Matter of taste, I suppose.
5 Black doesn't have 4K60. And at that point, you really need the new HEVC/H.265 codec as well, since the file size gets HUUUUGE(4K30 and 1440p60 at 60Mbps means ~4GB every 9 minutes or so). There weren't any SoC available with hardware HEVC/H.265 capability until very recently, btw.
And, while you're pounding away at those resolution/fps, it draws a lot of current, and that is super taxing to the battery. My battery lasts maybe 35 minutes with WiFi on, and it gets hot, further reducing battery capacity. Thankfully, trackday sessions are 20~30 minutes long, but I still have to recharge it between every session or swap between multiple batteries. I, once, (accidentally?) ran with charging cable left on the gopro on my helmet, so I guess I didn't have the battery 'range anxiety' that time. Probably not cool for POV cam under safety grounds, but probably viable for harness bar/roll hoop mount setup.
Ultimately, I'm waiting for 4K60 capable action camera with hardware HEVC/H.265 with ample battery in a nice form factor with good accessory support. I don't really care too much about image stabilization as long as the camera can shoot fast enough so every frame is sharp enough. And with good low light performance! Indoor footage at 4K is almost unacceptably grainy as well as blurry.
The GPS/IMU on the gopro 5 is actually supposedly very good, btw. At 18Hz, it beats the hell out of typical phone GPS (1Hz) and most entry level external GPS (5~10Hz).
I'm hoping GoPro 6 will have those features, or I'll give Sony or any one of those chinese companies a shot if they can manage to make a solid product. Either that, or I'll go with one of those 360 degree cameras since I'm a huge fan of VR, hopefully that can film in stereo for ~$500 range, which I think is a bit of a stretch...
On a side note, you really do need a fairly powerful computer to edit 4K/1440p60 footage. You also need an editing software capable of utilizing GPU. I've used Sony Vegas Pro(now owned by MAGIX), which barely supports GPU rendering, to edit my footage on a mid-tier desktop, and it routinely drove me nuts.