I think that we are about to see 2 very different strategies come to market with this.
Sony is an appliance company at heart. They like to release a product to market, milk it for a while, and then replace it. The idea of having a product and maintaining it with security updates, patches, adding features year after year for a whole console generation is not what they got into the console market for, and something that was never an issue until the PS3 (which they did a terrible job at) and the PS4 (where they learned from their mistakes). However, if they can release a new console every 3 years it will allow them to go back to their appliance roots; push out a product, patch it for a few years, and then push people to the next thing. I think that the fact it uses PC hardware is just what has to be done to keep developers in house, and that they will leave it for something else (like ARM) if they ever think that they can.
Microsoft on the other hand is actively bridging the PC and Console markets. Share a single core OS, a single store front, and a single CPU technology (x86) across both devices. Want a desktop UI and the ability to run non-store apps? Well then go buy a PC from one of their 'fine retail partners'. But if you want a respectable entry level computer that is essentially for gaming and media consumption, then I think they will be able to push out a new product every couple of years going forward.
The difference here being that when on the Sony side we will likely see fewer hardware releases, but when the PS5 comes out the PS4 will be quickly put on the development back burner. While on the Microsoft side, it is 'just another PC' and one of many PCs that players will be able to take advantage of. The OS will be able to be kept up to date for security and features, and the games will probably run better on older hardware for a longer amount of time.
That said, I have no idea who will be putting out the better products, or who will 'win the console war' that is fast approaching. Just from watching the history of things I think we will see Sony putting out products and sunsetting them, while MS will have products that evolve much more throughout their lifetime.
Personally, I'll continue building my own rigs every few years and use it for work and play.
Oh, and then there is Nintendo... Pretty sure they are going to release something similar to the nVidia Shield (the tablet one). No dobut it will be interesting, but no dobut people won't care enough to buy into their hardware anymore. The only interesting thing about Nintendo is that with recent changes to their corporate structure it sounds like they are also preparing to release a platform agnostic store front (think Steam or Google Play Store) that will run on other people's hardware. I may never buy another Nintendo console... but if they let me legally run their games on my PC or phone then you bet I will throw some nostalgia money their direction. Heck, I have quite a library of Roms, they may as well tap into the market of people like me and make some money off of it. I'll be more than happy to 'go legit' if they find an acceptable way to do it just as I have done with my music, movie, and other game collections.