That is a really exciting news. I hope it won't be cloud based !

I don't think the release will be next year, probably sometime 2017-2018.

They're not resting at the shadow of the PS4 success and are already investing in innovation for the future successor of the Playstation name.

Is it normal to start these things 4years or so before releaseing a new consol?
They really spend all that time on these things?

All gaming companies work on their next gen as soon as their current gen is released. This is the norm.

Considering how much Sony needs Playstation to be relevant? Yeah, this isn't a surprise at all.

It's way too early for them to be working on a parts list, so they are almost certainly working on technology. It's my educated guess they're working on HVDs and memory for uncompressed textures, but really that's anybody's guess.

Sony may be working on the PS5 already, who knows.

But this job listing gives no indication of that.

Looking at this section;

Preferred:
•    Current and next-gen game console experience is desirable (e.g. PS3, PSP, X-box 360 etc.)

If Current and next-gen meant 8th and 9th gen why would they have e.g. 7th gen consoles. More likely they meant current (7th gen) and next-gen (8th gen) so at the start of the ad when they say next gen they are meaning PS4 (8^th gen).

Also it's only a 6 month temp position so it might be covering someone who's taking 6 months leave, so they may have just copied the original listing from a few years ago. The last 3 paragraphs that mention the PS4 is just the standard job footer that’s on every listing.

For the PS3 for example they worked with Toshiba (and IBM I think) to make a new CPU, the Cell. PS4 was different as in they used existing technologies. It was actually only around 2 years before launch that they changed from a 4 core 3.2 GHz Bulldozer (AMD Desktop) to the 8 core 1.6GHz Jaguar (AMD Laptop/tablet). That was probably because Bulldozer was not quite as good as expected, so not significantly better (it might have been worse even) than the low power Jaguar, clock-for-clock. Jaguars are not designed to operate anywhere near 3.2GHz so I hope you see the logical option of the 8 core 1.6GHz which we have now.

I think you are definitely right when you say that some of the hardware for the PS5 is not released yet and is very much in development.

I think we could see the ZEN line of AMD chips in (some or all of) the next consoles. They are a significant leap over their Bulldozer predecessors and power consumption should be better. Maybe an 8 core 3.2GHz chip which could carry a 3x increase over PS4/X1/CELL. 

While I'm here, i'll also predict:

16GB fast unified RAM, giving 400-600GB/s bandwidth (enough for 4K60)

4-5 Tflop GPU (again, enough for 4K60)

All in a neat package that runs around 150w at full load.

This.  They (the big 3) even mentioned that that's how they do it way back.