I know the recent rumors indiciated to a modest refresh but I want to believe the next iMac will be bigger than we imagined. For one, Apple completely skipped out on not just the iMac, but the entire desktop line for the entire calendar year, which is completely unprecedented and which they've never done in history. I'd like to believe anyway, like the long and delayed MacBook Pro redesign, that a redesign iMac will follow suit, because of the same pent up demand and delay in releasing it. But I'm probably setting myself up for disappointment
As for the keyboard, I think many people have been wanting a backlit wireless keyboard for some time now (myself included). I guess if Apple wanted to make a big splash with a wireless Touchbar, then it would be great to see the Magic Keyboard 3 get that plus backlit keys, but I'm not going to hold my breath.
And I actually personally prefer the white keys, but then I also want a matching white bezel on the iMac too. So that said, I get the desire from people to have black keys to better match the black bezel as well as the MacBook counterparts. But it never made sense to me anyway. Why Apple chooses to make gold and rose gold finishes with white bezel fronts for its iOS devices while not doing the same for the MacBook.
Anyway, if Apple were to offer a space gray iMac with matching space gray keyboard and black keys, I think a lot of people would be happy. Backlit keys would be icing on the cake.