Information on board partner 4090s is now available.  It is clear why EVGA (which had 40% of the North American market) got out of the GPU business.

4090s are 4 slot cards if air-cooled; one by Zotac is a 5 slot design.  They are coming with supports to hold the cards up so they don't bend the PCIe slot.

I can't see people buying these in mass.  The 3090's will give a better price to performance ratio.  Nvidia has overbought on TSMCs 4nm process and TSMC isn't letting Nvidia cancel their orders.  There is going to be a mountain of 30 series of cards (most board partners are sitting on up to a year's worth of 30 series cards) and an over supply of 40 series chips.  I suspect that most of the 40 series chips will end up in data center products rather than gaming cards.