Yes, it split the Userbase, people use Phones to Simple things that even a Toaster can do,  being Unable to play Triple A Games, is unacceptable for a Console, a PS4.5,  means, less games for both systems, and worse games because of optmization.

It wouldn't suprise me if it was just a 4k blu ray player with 4k netflix support and possibly 4k cut scenes in games.  Basically hdmi 2.0 and hevc codec.

You really do not seem to understand how this works......... Upgrading hardware does not change anything when the software is the same. It is the same as upgrading your CPU and GPU on a PC your old games will still work and the people with the old CPU and GPU will be able to play the same games with lower settings/resolution. That in no way "splits the base"

No, is not the same, Developers would need to work more and would need to move people for Quality control for each version of the game, this isn't  like the PC, the Players of the console version don't have the option to change settings, the Developers are the ones who need it, the Games would look worse on the First PS4, and the Power of the PS4.5 would never be used.

Developers have total control to turn settings on and off and change the resolution. Would not take anymore people than they already have.

If the PS4.5 DOES NOTHING but keep the FPS from dropping in some games then that would be enough for me but I expect its primary use will be for adding AA and more effects as well as better framerates in unlocked games

Would take more people and Time, isn't like 1 Click and is over, they would need to make a Team to work on the Newer model, the Team would be made of  either new Employee, or of the Development Team of the actual game, and this would make the game look Worse,  take more time, and more money for Developers.

If Playstation 4, like became Upgradable, and the Xbox One, have a Middle-level, and a High-level Model, Developers would need to move people for those versions, this would piss the hell out of the gamers, and would piss off developers, All the developers would stop making game for Console, and make PC-Only, because they woud only need to developer for 1 Plataform, and the Gamers would  jump for the PC Market, is better pay 1000US$ on a PC, than have to Pay 300-400US$ every 2 Years to play games on a Decent level.

Adding AA and effects would be a simple piece of code.......

That is not going to happen. You seem to be confusing a minor upgrade with an entirely new system.

The PS4.5 is going to be in the vain of a N3DS it is going to make your experience better while keeping the same games. IF the PS4.5 has exclusive games that the PS4 does not get before the release of the PS5 then I will agree with you that, that is wrong

New Nintendo 3DS, have Exclusive games that the older versions don't have, and is just a Minor Upgrade, also Monster Hunter, does not run well on the older versions, this make you need to upgrade if waant to play the game, also the "Upgrade" of a Home Console, if isn't just a Slim Version, would be much more than just the New Nintendo 3DS, had.

Thats because:
1.) The 3DS is a POS in terms of hardware and can't run anything advanced
2.) Nintendo allowed it.

If Sony mandated that the game be built on the PS4 first with upgrades allowed (optional) for PS4.5 then your concerns are moot and just fear mongering. Just remember they have to certify any and all games on their platforms.

When a game comes out only for PS4.5