The PS3 was finally jailbroken five years after launch (it was launched in 2006 and jailbroken in 2011). The PS4 looks to have continued in the rule-breaking footsteps of its predecessor, as a jailbreak has also been released for the system, about five years after its announcement.
The jailbreak is based on an exploit in the 4.55 firmware, and a number of developers have taken the opportunity to delve into the various possibilities that such an exploit offers—game dumps, homebrews, Linux installation, etc.
Of course, users on firmware versions higher than 4.55 will not be able to enjoy the perks brought about by this exploit. While staying on firmware 4.55 allows users to gain better control of their consoles, it also comes with the consequence of being unable to use any of Sony's online services. The PS4 is currently on firmware version 5.05—5.5 is still beta— though, and there is word that exploits may be coming to that firmware version soon, so those who want to move to the dark side in the future will be better served staying on their current firmware.