Summary article, what we know so far about the Neo.
http://www.eurogamer.net/articles/2016-06-23-ps4-neo-release-date-price-specs-and-everything-we-know
Excerpts...
Neo Boost
CPU 1.3x
GPU 2.3x FLOPs
Memory 24% more bandwidth, 512MB more useable memory
In short, the PS4 Neo is different to the existing PS4 in the following areas:
- Graphical and performance improvements to supported games when played on Neo
- 4K native output of select games, and the ability to upscale to 4K of others
- 4K video support (specifics, including UHD Blu-rays, have yet to be confirmed
[....] Until then, we know that improvements will range from the following for Neo-mode titles, depending on the game:
- Mandatory 1080p minimum native display resolution
- Higher frame-rates
- More stable frame-rates
- Improved graphics fidelity
- Additional graphics features
What we don't know about the PS4 Neo yet:
- Whether PS4 Neo will have a UHD Blu-ray drive for 4K movies
- Whether the physical appearance of the hardware will be different
- HDR support, something that is coming to Xbox One S (read what HDR means for games and movies with our dedicated article)
- Whether background media functions will improve; Sony leaks have suggested but not confirmed 1080p gameplay recording support on Neo systems
- Specific improvements to PlayStation VR games, or whether the headset's external processing unit will be integrated into Neo hardware
- Hard drive space increase in Neo models
PS4 Neo games: What software will be improved on the new system?
From October 2016, all games released on PS4 must offer a Neo mode to offer visual and performance improvements, whether it's a resolution increase, or new graphical features. While this surely means many of this year's biggest releases will have Neo modes - such as Gran Turismo Sport, Watch Dogs 2, Dishonored 2 and possibly the PSVR line-up - there have been no confirmed titles yet by first or third-party studios.
Developers are welcome - but not required - to add 'forward compatibility' patches to their existing PS4 games...