It seems fairly obvious to me.... 1 card slot for the non-pro model, leaving a good amount of room and reason to have to buy the pro model. I think shot themselves in the foot with the A7iii /r being so capable, it's difficult to justify the a9 in my opinion.
Furthermore, what reason are people actually upgrading for? Let's think about this, if you shoot weddings with Nikon slr's.... there is no need to change to mirrorless is there? Especially given the lens line up at release is not really sufficient for a pro wedding photographer.
If consumers are looking for a reason to change to mirrorless, for whatever those reasons are, then this may not convince those.
However, those that are looking to buy their first camera, or are looking to buy 'a nice camera' will probably buy this in droves.
The release of the new pf 500mm suggests there is a lot of life left in the f mount.
Perhaps Nikon is planning on running both formats? I can't see sport / wildlife photographers changing from their D5's any time soon....