I guess I was in the minority in hoping that the successor to the GRD IV would have a smaller 1" sensor and a small built in VF. They probably could've done it at the same size too, with the VF.
While I agree that an external OVF would be less ideal on the GR than on the GRD, due to the larger sensor, I think it'll still work out nicely for street work, set to f/8 and snap to 1.5m.
I use a Voigtlander 21/25 VF on my GRD IV, and I think I prefer it to a 28mm VF. I get to see outside the frame, and it works nicely with the 21mm EFOV adapter too.
The new GW-3 doesn't look much larger than the GW-2, though I can only find one picture of it so far, and it's not a great angle. But if it's anywhere near the size of the GW-2, I think that might seal the deal for me, since it's probably one of the most compact ways to get a 21mm fast-ish EFOV.