Even the Atari site is announcing the Sept. 23 release date

[Sandman]

Link1
Link2

Link2 is not working at the moment - they are probably having some server problems.

6hrs of gameplay hours require to finish all sidequests available, and take all battles in the map. But this is obvious What's more you can choose to play all three hero classes.
I can't tell much about english demo. I've only heard that it is supposed to be released next week Polish one is out there since yesterday