It won't! The 4090 (5090?) Will just be the absolute worst and we will see the efficiency game do a full 180° with AMD on top of the game, having wildly more efficient GPUs than NVIDIA, but that's because NVIDIA simply can't do better, this is just GTX 400 Series all over again and NVIDIA will get their together one or two generations down the line. We will probably still see slightly higher power draw in general but not 600W for all top of the line GPUs going forward, it will probably come down to 300W next generation around.
Uhm what?... It usually doesn't matter that much wether the fan is facing up or down in a case. It's just usually preferred to have it facing down, so that the PSU draws fresh air in and then exhausts it out the back. That way it has it's own little eco system basically. Doesn't mean it HAS to be this way though.
And according to Google images, when it's installed in the bottom back part of a case (which they normally are in cases, ie for example the Fractal Torrent has the PSU mounted in the top of the case) it looks just fine to me?:
No. They are not. It mostly doesn't matter because PSUs are very efficient these days. Turn it the way you want. But if your case is on the floor or on thick carpet you should always turn your fan top. Especially if you have pets.