You know, with how quickly these consoles have started being profitable for both Sony and MS coupled with how quickly PC components get replaced by faster parts I could see them shortening the cycles back to 5-6 years like we have had in the past.

I could also see it being more likely they will just iterate on the current consoles with faster components and add some minor changes to the systems rather than go all out and launch whole new consoles.

Either way with compatibility issues most likely gone for the foreseeable future console gamers will once again be able to keep their game libraries (digital and perhaps physical too) and continue to play them on the new consoles. Backwards compatibility is more important today than ever before with digital being much more widely adopted and people wanting to have some feeling of ownership over their digital purchases.

There's a better chance PS5/XB(2?) will be fully compatible with PS4/XB1 with the same x86 AMD Fusion-ey architecture.

That's exactly the problem. They are concentrating on graphics instead of resolution and I don't see them going away from that for a while. To be honest, I don't even think 4K is necessary yet, considering we barely get 1080p and we can live with it..

People who like this idea are gaming on PC as we speak.

There are many other reasons.

What "sooner" exactly means? 2017? Cause anything from 2018 is expected.

What people are doing on PC right now has nothing to do with what Sony or Microsoft will do with their consoles..   so.. that is not a reason in the least. Console gamers and PC gamers are NOT the same audience except for a small group. Most console gamers are unware of how PC gaming and graphics card etc work..  

Saying "There are many other reasons"... is also not one... So you have said ZERO info on why you think it will never happen.     

With mobile gaming on tablets and phones continuing to RISE it will make LESS sense for console developers to poor millions into new gaming systems. The natural evolution upgrade path works out best on SO many levels for them.

5 or 6 year cycles sound good to me. I like the experience of getting new consoles. They can still sell for years after if they get support like PS1/PS2 did. PS3 & 360 will also pass 10 years before discontinued. Wii is the odd one out for a successful console that fizzled out in a shorter time.

2017 THE EARLIEST.

Since making games is more expensive I can't see this generation being shorter than the last. The speed at which they put out titles hasn't improved and may have slowed so I can't see them breaking even on those R&D and production costs faster than last gen.

This is pretty much exactly what they should go with. The biggest reason for the dearth of games in this generation currently is the lack of a sufficient install base and the developers, many of whom scared not to sell enough volumes, are wary until the consoles build a sufficient user base.

Having a fully backward / forward compatible console architecture in the future will make the transformation seamless. The developers can continue developing whichever platform they like to cater, the games would work both in last gen and next gen consoles because of compatibility. They will probably include modest improvements and tweaks on the next gen consoles, but the differences will gradually be larger. By the time the next-next gen arrives, the current nextgen would be maxed out, and we could see a similar shift all over again.

This is actually the best of both worlds.

* Have a fixed architecture and hardware, which is upgraded only at long eintervals

* Platform compatibility and digital dependence insures "network effects". Once a playstation consumer, you're most likely to be a playstation consumer next period because of all past purchases, which are cross generation compatible.

* Hardware spec differences start to matter less (in the Long Run) since they will be upgraded in time with full backward/ forward compatibility and dimishing returns.

* Brand loyalty, solid platform metrics, network effects, compatibility, exclusives, communication etc will start to matter a lot more.

Basically both PS4 and XB1 are the steps at the right direction. They are a specialized pc-based platforms, which are hopefully forward compatible, and declining costs.