hi mate,
if you check Google there are many reviews of the 920 and also reviews comparing its performance against the N8 and other phones on other platforms.....there are a series of excellent articles over on AllAboutWindowsPhone.com comparing it with the N8. I myself have come over from my older N8 to the 920 and I do find it a great phone all round. It has been an excellent experience with the apps, and fluidity of the operating system, and overall ease of use, the music experience and the camera performance in low-light has to be seen to be believed.
I do admit though, that it's not everyone's cup of tea, the camera on the N8 is excellent especially with the xenon flash. I went from the camera on the N8, and had the N9 and had such a horrible time with it I sold it within two months and went back to the N8, up until the time now where I am using the 920 as my daily driver.
Obviously there are no details, or speculation, on whether Nokia will release a 'better-specced' camera in the near future, though Nokia has stated as recently as the CES show in Las Vegas this week that there will be more great things coming with imaging in the future. After the N8, and 920 I eagerly anticipate this, and I do indeed rest confident in the fact knowing that my next Nokia will be a great device with a great camera!