Firstly, the constant trading in and upgrading that you're proposing makes it sound like the mobile phone business which IMO is a total shitfest. Going down that route and it won't be long until the pricing is the same. PS5 at $2000 dollars unless you get a monthly subscription or some stupid shit like that? No thanks.
Secondly, that's a very dodgy conclusion you have there that I don't agree with in the slightest. While I would agree with the thread title that it's not necessarily a bad thing, trying to argue that it's a good thing instead? Nah, not fooling for that.
Although I agree that a business model like that of smartphones would be terrible, having to wait six years for a new model smartphone would probably be even worse. That would be like going from the first Galaxy S to an Galaxy S7 in one go. Why not atleast something like a Galaxy S3/S4 iafter three years, especially if that first Galaxy S would receive new software and updates for a total of six years?
Also with or without a PS4k, a PS4 would be worth roughly the same after six years. So why not offer the option?
Smartphones are not consoles, whereas the PS4 is solely owned, developed for, manufactured, and developed by Sony (and the companies they contract), smartphones have millions of people developing for them, hundreds of companies manfacturing and developing for them, and many big companies like Google, Apple, and Microsoft working on their oses and such.
Furthermore, consoles are luxury products they are not necessetties like smartphones are. So upgrades are unlikely and if that is the case then Sony will end up wasting money on R&D, manufacturer, and development of the PS4K.
This leaves Sony with three shitty options:
1. Stop dev and distribution of PS4 to force people to upgrade, thus alienating their existing base and ruining a lot of their customer confidence and end up flopping ala dreamcast
2. Incetivize PS4K by giving it exclusives, thus fracturing their entire base, ruining customer confidence to a lesser degree and selling less on both platforms while still dealing with the expenses for launching and manufacturing the PS4K
3. Do both and give the PS4K no incentives, base remains intact, customer confidence is shaken not stired and they sell less on both platforms, but then have to deal with the expenses for launching and manufacturing the PS4K
These are all the results of making the PS4K a significantly upgraded PS4 rather than a slim PS4 with just 4K blu-ray capability.
This is why it makes zero sense to compare the smartphone market to the console market:
phones aren't made for apps, apps are made for phones
consoles are made for games