According to this, it will be announced 2010-08-19: http://canong12.com/
London, UK 19th August 2010: Canon
today announces the launch of the
feature packed PowerShot G12
As this information will be useless in only two weeks, and information about specific camera models is available elsewhere, I'll try to add some more general thoughts:
If there is a new camera release imminent, you may want to wait for it, otherwise it's just a question of whether you want a camera now or if you want to wait for some specific feature.
There are new and better cameras released all the time, so if you want to wait for the best camera, you will wait forever. You just have to settle for good enough. If you buy a camera, and see that after a while there is a new and better model released, that doesn't make your current camera any less good.
You may even look at buying the older model when the newest is released, or a used camera. You may even find the previous model in a more expensive segment at the same price as the newest in the segement you first aimed at.