Wait for the GH5, it has a good possibility of having IBIS in video mode which could work well with a lot of existing wide primes. Wide lenses don't often benefit much from IS anyway unless you're shooting handheld photos in low light which is done better with Olympus 5 axis IBIS cameras.

@brianc1959

Is it worth additional hundreds of dollars and increased weight and size and worse handling compared to if there would be a native m4/3 option? Still Panasonic native lens would be very expensive too.

How about Sigma 18-35 f1.8 + speedbuster?

@Vesku For many people the answer is yes.

The Sigma 18-35 + Speed Booster (12.8-25mm f/1.2 for 0.71x ULTRA and 11.5-22.4mm f/1.1 for 0.64x XL) are amazingly good combinations for the GH4. However, although you do get fast AF you won't get IS because the Sigma lens has none.

why not a used 17-50 of tamron or sigma with speedbooster, they say the IS is better than panasonic 12-35 and it costs the same, I don't have 12-35 but I also have seen that it has problem with exposure when zoon in/out that both tamron and sigma and probably canon zoom perfectly

Still 50 time less than buying a Cooke, Angenieux or Arri-Zeiss Master Prime. :)