I'm glad Canon cut the ISO at 6400, and has a native ISO 50 with an expandable 25. This is clearly a studio unit (perhaps some solid landscape applications as well) that will have some killer low ISO performance.
I just hope it's real!
I hope it's REAL too!
But Canon has to make some serious improvements in their hardware to reduce the (patterned) read noise that is the bane of their current technology.
Without a significant reduction in read-noise, the lower ISO settings will be useful for wider apertures, or slower shutter speeds, but without a commensurate improvement in DR or need for extra digitizing bits.
DR should increase by about the same amount as ISO decreases (stop-per-stop) but if you look at Canon's measured DR curves, they're pretty flat from ISO 800 down. E.G. The 5D3's DR is only moving about 1 stop despite 4 stops worth of ISO change.
Recent SoNikon's DR curves behave as they should, DR increasing equivalent to the decrease in ISO.
If Canon can fix this, for a new high-MP body, they'll please a lot of their current customers who've been hoping for such an improvement for years!
And I also hope that, if they DO accomplish this, we aren't hosed 10x as much $ as such DR technology can be had from competitor's products for as little as $500 in a consumer crop body.