Several sites seem to be reporting PlayStation 5 'devkits' being sent out and detail the power and capabilities of the system with relative precision. The sites have previously been known to somehow know the specifics of certain products.
We know the PlayStation 5 is in development, but that Sony were sending out devkits of the platform to a certain number of developers, not many people knew. Of course, the PS5 is a stand-in name, as the true name of the console is yet to be revealed. The system might even be released in 2018, as sources state.
Nothing is for certain, but the system will apparently be built upon AMD's Navi architecture, but the development of that technology is not yet complete. It will feature an 8-core AMD Zen central processing unit, which is AMD's newest tech for CPUs announced in March 2017. If true, this will enable the console to run graphically more challenging games with much greater ease and speed.
Additionally, apart from the CPU, mentions of a GPU have been revealed as using the previously stated Navi architecture, however this could be a far-fetched guess since that tech isn't out on shelves yet for PC users, let alone console users which use tried and tested graphics units to assure quality.
Sony is going to be pushing the virtual reality side of gaming a little further, as the console is reported to have VR support baked into the silicon of the system. This suggests that Sony sees the opportunity of VR and hopes to further the generation's advancement into the future.
This reveal coincides with CD Projekt Red stating they might even be developing their newest game Cyberpunk 2077 for the next generation of consoles as well as the current one. What this means is CDPR have probably received a devkit of the PS5 and are using it to develop the game for the next generation.
The source, SemiAccurate, is doing mostly guess-work. However they state in their article that many times before they have been proven right while others laughed at them. The writer of the article has a certain overconfident tone when speaking of the PS5's specs.