The next generation of the Sony PlayStation would be released in 2019. In fact, Microsoft will likely follow the year after that with its new Xbox. For the moment, PS4 is still making lots of money. So, the developers might use this for their own advantage for now until its successor will take its place.
However, the PS5 has been speculated to be the real 4K device. Therefore, it might not be launched, unless the momentum of the PS4 sales would slow down. If the PS4 sales would slow down in 2019, then the PS5 will probably be released in 2020 instead.
In fact, other experts say that the 2018 launch of the PS5 might be a bit premature, after the performance of the PS4 to date. However, that would pose a problem if Sony delays the release of the PlayStation 5.
This is because Sony might lose the exclusivity of their standout feature to the Xbox One X. For the time being, the PS4 Pro and Xbox One X may have extended the life-cycle of their original consoles. This includes the Nintendo Switch, which is one that might be around for some time, unless sales would drop down dramatically.
Nevertheless, the Nintendo Switch is currently underpowered by the PS4 and Xbox One. So, even if Nintendo would follow suit, it might just not expect bigger sales results compared to these big competitors.
The moment PS5 will confirm its release date, one killer feature will also be released. This will be the PS VR, which have continued to sell even when stocks were limited. Microsoft, on the other hand, has been looking forward to release something. (Zolpidem) There will be a possibility that a mixed reality capability will be released by Xbox One X, since it was first advertised to have this feature. But, no confirmation about this update has been made yet.