The UK price will hopefully be around the same price when the GH4 arrived just under two years ago…£1550 – £1700. Remember although it has an impressive 10bit 422 colour space this will not be available in 4K 50p mode. I bought the 12-60 lens with my GH4R and its a great lens apart from the f3.5-5.6 aperture, this was a major disappointment after the f2.8 constant aperture 12-35mm lens. No info on a dual card slot, but with Olympus at their heals hopefully Panasonic have added a dual card slot.
The Olympus OM-D E-M1 Mk11 (£1,849) has a dual card slot, 4K and a very good stabiliser plus a headphone and mic socket. I have 5 Olympus lenses (3 Pro) and they are the best money can buy.
It’ll be interesting to see comparisons when the GH5 comes out.
On paper the GH5 for me wins out with 10 bit 422 and a pro audio module.