5.50 Beta detailing the features, which has since been followed by both the PS4 5.50 OFW release and a PS4 5.50 WebKit (Userland) Exploit.
Today mainstream news media outlets including Destructoid, IGN and VG247 report that signups for the PS4 System Software 6.00 Beta Firmware update are now being taken in some regions including North America (Working Link via GrimDoe) and Japan with Europe not live yet.
Some PS4 Firmware 6.00 Beta 3 Screenshots of a cleaner UI have also surfaced, and this comes proceeding the release of the current PS4 Firmware 5.55, and according to reports the Japanese signup page states testers are being accepted through July 27th providing applicants are over 18 years old and a PlayStation Plus or PlayStation Now subscriber.
While the pages above appear to be taken offline at the moment cached versions still exist, however, it likely won't be long before Sony makes an official announcement asking for 6.00 PS4 Beta Firmware testers... we'll update this article again then!
Download: 600.elf (Decrypted - 19.26 MB) / 600.i64 (Decrypted - 133.18 MB) / Shared Folder / Shared Folder (Mirror)
PS4 Installing 6.00 Beta/Downgrading To 5.55
Warning: If you're on a jailbroken PS4 console don't update to the BETA as @DEFAULTDNB confirmed the following via Twitter, to quote:
"You can only downgrade to the current highest released OFW (in this case 6.20) regardless of what firmware you updated from. It's hard coded now."