The userbase split from past does not work anymore, PS1 to PS2, PS2 to PS3, PS3 to PS4. It was essentially a total reset to the userbase but it was possible since games were cheaper to develop. Look at this gen, early games had to be developed cross-gen and PS4 versions were heavily held back because the spec and architectural difference between PS3 and PS4 was so big. Simply, PS4 userbase did not allow game development alone.

Your example of PS4.5 development cost being additional 30 million is ridiculous. Developing a PS3 and PS4 version of a game was expensive because of the extreme spec difference but even that is nowhere near your figures. For PS4 and PS4.5 it would be comparable to making a PS4 and XB1 versions and most likely even easier. Sony could make standard tools for developers and then making a PS4.5 version from PS4 version would only require minimal work.

And who would buy a PS4.5? No, not everyone who was going to buy a PS4 would buy a PS4.5 instead. For example, PS4 could be priced at $249 and PS4.5 at $399, the price difference would attract different audience and give the option of lesser/better graphics to the consumers. Let's add competition to the discussion. What if Nintendo or some other rivaling company (Apple, Samsung, etc..) released a console in Q4 2016 which was more powerful than PS4, then Sony would have a direct counter with PS4.5. Thing is, 6 years is an eternity and opens doors for other companies to enter the console market or at least gives them more opportunities. With upgradable model Sony can react to competition much faster and that is what is going to be needed in the future in my opinion.

Just like how Xbox One fragmented the Kinect base and the post-Kinect removal users for that graphical upgrade?

I am all in for an upgrade :) I bet this new PS4, will replace the current PS4, but all the games made will be able compatible with both.

the PS4 is a console everyone is loving, so why divert people's attention with another one.   I think Sony is very clever to continue naming the new console as PS4 since it will ride the momentum the console is currently having.

Obviously they wont screw "early" PS4 adopters, and all the games will be able run on both PS4 consoles.   Since it will only have additional RAW power, and not a different arquitecture, compatibility with both consoles should be easy.

games will be compatible between both consoles so upgrade wont be needed, unless you want better graphics.

I Only said that if someone purchase a Playstation 4.5, is because already was interested on Playstation, so would purchase Playstation 4, if there was no Playstation 4.5, amd this is Ridiculos, the Cost of Development would be Atleast on the Level of a Handheld game, for the different versions, and this is more than the Entire cost for a PS2 Game.

Look at the Console's Early Top Sellers, and compare, we Have more than 3, 10 Million Seller on Consoles, in just 2 years, this is something that was not possible back then, the Games are selling more than before, Make Consoles, also make the games with better otimization, because everyone have the same Hardware, is much better to make a New console, and Begin the Generation from the start, than just upgrade it, in the end the 2 are nearly the same, but the Generations, are better for Consumers, Developers, and the Games, so is good for everyone.

In Consoles, Power isn't what is the more Important, People only buy consoles for the games, a Console Slighty more powerful would not interfer on Playstation 4, The Install base, is what matter the most, if Someone release a Console for the 8 Generation on the middle of it, will only lose the war, because the Install Base, would not be enought, and you would lose every game for your Rival, so is better wait and start on the beggining of the next generation.

The Playstation 2, was one of the weakest consoles of the 6 generation, but with much more games, and sold more than 3 Times the sales of the other 3 Console competitor together.

Xbox One isn't selling less than Playstation 4, because of Playstation 4's power, is because Playstation 4, have much more games than Xbox One, and have a future with much more games, while Microsoft, does not give this kind of Safety, when someone purchase a Console, is like the people is making a Middle-long term Investiment, Nearly nobody can aford to have more than 1 Console, you would need to purchase more than 1 console, pay PSN, and Xbox Live, and buy the games for those consoles, this is much expensive, so on the Beggining of the generation, everyone only pick 1 Console, and if have no incentive into buying another when it became cheaper, they will not, because the Next Gen, would be just around the corner, and the Cicle once again start.

The 40 Millions of Playstation 4's User, give much more revenue than the 300 Millions of Steam's User, so this thing of Upgradable  does not means that the People will Upgrade and will play your game, some games  would look Poorly on the old versions of the console, so less people would purchase it.

Playstation 3 + Playstation 4 + Playstation Vita, gave 12-15 Billions of Revenue for Sony, Steam, gave 2-2.5 Billions of Revenue for Valve, more than 500 Millions coming from microtransactions of CS Go, and Dota.

Console gamers spend much more money with Triple A Games, and if all the companies start to make the Console Market, like the PC, this will Piss the ones that  like the Console market, that is the Majority of the triple A Players, the Heavy majority.

This really makes no sense, and would Break the momentum, and would kill the console market if this is a move that all the 3 will make, The Momentum would be able to continue with the Playstation 5, make a new PS4.5, Would send this mensage for consumers "So they don't really care about the early adopters, so lets just wait until the Ultimate Version is out", Microsoft, also made the same mistake, with too much Price Cuts, now everyone expect a price cut, before purchasing a Xbox One, is aways like this the Cicle, Xbox One Launch >>>>>>>>>Price Cut>>>>>>>>>>>>>>>>>>>>>>>>>Sales up>>>>>>>>>>>>>>>Sales Down>>>>>>>>>>>>>>>>>>>>Price Cut>>>>>>>>Sales up>>>>>>>>>>>>>>>>>>>Sales Down>>>>>>>>>>>>>>Price Cut.

they need to be aware of that you are telling for you consumer, or otherwise they will be Doomed, the Lead-man in each company need to think about this.

All 7 people who have a 4k TV are going to really love this.

I feel is plausible, make completely sense. VR requires power, if Sony is serious about VR, this would be a logical step, maintaining the current marketshare of PS4 , but selling a upgrade not called Ps5.

I doubt any of that. Sony gains nothing from doing a PS4.5 and has everything to lose from a move like that. This is most likely some sibling theory that spawned from the unlikely idea that MS is gonna create upgraded versions of the xbox one or allow people to upgrade the xbox one. Why would sony or ms try to emulate steam machines when they didn't really do well at all? It makes no damn sense to have tiered consoles.