From what I heard the new housing is exactly the same as the old one, the cameras are the same dimension and the FOV is the same, the backpacks work for both and even the battery is the same. You do get options to use 90, 127 and 170 FOV in 1080p30 and 720p30 but I think 720P60 is limited to 170 FOV still, I found using the original gopro HD the 1080P30 mode gets more noisy earlier then even 720p60 if light isnt perfect which is why I shoot most of my video in that mode.
In theory the 30P mode should let in more light then 60P but in all my testing so far I haven't found that to be the case between those 2 modes. When I get the new camera it will be interesting to see how the faster processor, and bigger sensor help out underwater but I would expect 1080p mode to be a little more usable in more conditions then the original gopro.