Don't hold your breath re. I.B.I.S. I have a feeling that this might well become one of the distinguishing features for the FX line - DX: compact, maybe even elegant/stylish/hipster (pick your moniker), affordable, truely portable; FX: enthusiast/professional level, with full sealing, I.B.I.S. etc.
I honestly find it sort of strange that people assume Nikon will simply continue their former strategy - isn't it time to change it? What I see on the DX timeline points towards (advanced) entry level - and in my opinion, there's absolutely nothing wrong with that, especially if entry level means Z 50 level solid. The Z 50 is more than a match for the D5600 and approaches the D7500 in many ways while being clearly more compact and more affordable than the latter. Would it be nice if there was a D500 replacement? Definitely, and I think there will be, maybe even including I.B.I.S. to make it more of a hit, but I'd not be surprised if this was low priority at the moment. There are market shifts to consider, and I think Nikon does pretty well in terms of filling the remaining niches. The Z cameras offer a lot for the money and a more keenly priced than the competition.
The Z fc has enough to distinguish it from the Z 50 in my eyes - it may be the even better EDC, but less capable as a "second body" (which the Z 50 is for me - including its additional reach with FX lenses). It's also more desirable for vloggers (not that I am one, but who knows where the fancy might take us). I laid out my view on it in a different thread already.
I'll pre-order the Z fc with the 28mm - it hits the spot for me; my Sony stuff (and a whole host of various lenses all over the board) is scheduled for trade-in, and by the time the camera becomes available, the whole Fuji system may be, too. Not because it's bad (it obviously isn't), but because I'm happier with my Z system than I've been with either Sony (that's not difficult, given their handling paradigm) or Fuji - which I'm surprised about myself, but that's how things are. Maybe a X-S1 could have changed that - but I'm not going to try that now the path appears clear: The FX system is where it's at for me, the DX stuff being a nice and fun complement - I don't think I'll put a lot of money in it anyway, but so far, it has paid off hugely.
M.