The new Nikon D5 goes up to iso 3 280 000 and luckily competition means manufacturers will keep pushing the boundaries of high iso performance.
Many people have made comments in the past that nobody needs iso 1 000 000, and that "high iso's are getting ridiculous" in new cameras. I don't agree and feel that much of the opposition is due to fear of change. In 10 years when we have a clean iso 1 000 000 people who are born in that time would feel very limited by only having a camera with a clean iso 10 000.
Let's do some calculations, supposing that because many people like to shoot with their lens at its sharpest with a large depth of field around f11, and a safe setting for minimal movement is 1/1000th sec for most practical focal lengths we shoot with.
Let's go to an EV of -6. You're outdoors, nice clear night with lots of stars [in 20 years we will be discussing shooting landscapes on an overcast night and how far we can push the iso] and you want to shoot at f11 and 1/1000th sec, maybe catch a bat in flight by chance as well :)
EV-6 means f11, 128 minutes and iso 100, or 1 minute and iso 12800, 1 second and iso 768 000, 1000th sec and iso 768 000 000.
Manufacturers will continue to push the limits of high iso and one day, when we have a clean iso 768 000 000 who wouldn't embrace the prospect of going for a walk at night and snapping a few milky way photos without having to carry a tripod around. :)
At one dance event I shot with with my D40 at f2.8 1/125th sec and iso 800, 10 years ago.
Now if we had a clean iso 1 000 000 that could have been shot at f11 and 1/1000th sec.
Of course many will oppose that idea, some will even argue that they like having the blurred background that f2.8 yields - well they can still have that if they want while others can embrace the prospect of a large stage performance and being able to get everything in focus at f11 and 1/1000th sec when they want to. That's the beauty of it, you don't have to use it if you don't want to - just don't whine about it not being necessary because there are many of us would love to have a clean iso 1 000 000 - while we wait for the clean iso 768 000 000.