One question - and a tidbit...
18 Sigma lenses in the near future? Unless Sigma has a much bigger lens design department than I think they do (or than Canon, Nikon, Sony or Fuji have), at least most of those are going to be DSLR lenses with the adapter built in, not dedicated mirrorless designs. Are any of those 18 lenses going to be true redesigns?
It's easy enough to take a DSLR lens, stretch it an inch on the back end with no glass in the back, and call it a mirrorless lens, while it's a lot harder to redesign a lens to take advantage of a new mount. The mirrorless mounts are similar enough that a true mirrorless lens should fit them all (with the possible exception of the narrower FE for some lenses). They'll probably all come out for multiple systems - there are already 14 or so FE mount Sigmas, all of which are stretched DSLR lenses (to Sigma's credit, they admit it, placing the lenses in their DSLR series despite the mirrorless mount).
I really wouldn't call a stretched lens anything different from a manufacturer adapter lens (F on Z, EF on EOS-R, A on FE). There is a difference between a stretched or manufacturer adapter lens and a cross-adapted lens, because both the tolerances and the electronics can be issues with cross-brand adapters, especially the cheaper ones.
DPReview mentioned (with no source for their information) that the Panasonic sensor is NOT BSI... This indicates that it isn't a Sony derivative. What is it? Sony has had a one or two generation lead over any competitor in the large-sensor game (notably Canon, but also the various sources of Leica's sensors). If this is a sensor that hits the market behind the times, that's a significant disadvantage.