Finally - the $659 Metabones Canon EF to Blackmagic Pocket Cinema Camera Speed Booster Adapter is available for pre-order at Adorama!
Now, Canon shooters can transition to the $495 BMPCC with straight-out-of-the-box 10-bit ProRes and 12-bit RAW recording for a little over $1100 without buying new glass. I'd say now is the time to leave 8-bit h.264 behind.
Sadly, this adapter should not be used with the GH4 or other micro 4/3 cameras due to possible shutter damage. Hopefully, the vanilla Canon EF to micro 4/3 adapter is coming soon.