We have finally some more reliable news about the GH4 availability. Preorders in US store will be accepted from late March. And actual worldwide shipment is scheduled for late April. Also BHphoto (Click here) confirms the final shipment date info while Amazon (Click here) still shares no detail on that.
And here are two more GH4 related youtube videos from Kenmorecamera:
Hands On with the GH4 at Kenmore Camera
GH4 4K Video of Kenmore Camera