Following Sony's PS4 Beta Signups, the PS4 Beta PUP Updates and PSN Online ID Change Feature that was discovered today the latest wave of PlayStation 4 Beta 6.50 Firmware invites are going out to select users who previously joined their BETA software program. 
A copy of the invitation can be seen below, and to quote from XtremePS3.com on the PS4 Firmware 6.50 BETA changes detailed thus far:
The changelog for the beta does indicate that two new features have been added to the update:

Download: HERE - Must be in Sony's BETA Program as DEFAULTDNB confirmed installing using THIS legacy method no longer works from ps4.update.playstation.net and ps4.update.sonycoment.loris-e.llnwd.net via @Sametto Chan on Twitter.
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."
PS4 6.50 Beta / New Features
JSC_ConcatMemcpy_InfoLeak Patched in 6.50 Beta 
From Pastebin.com following the previous developer build strings:
A copy of the invitation can be seen below, and to quote from XtremePS3.com on the PS4 Firmware 6.50 BETA changes detailed thus far:
The changelog for the beta does indicate that two new features have been added to the update:
- You can now choose 720p when you broadcast using Niconico Live. This service is only available in certain countries and territories.
- You can now change the button assignment to perform “Enter” operations from the O button to the X button. This can be changed from the [Settings] > [System] menu, and is only available for specific countries and territories.
Download: HERE - Must be in Sony's BETA Program as DEFAULTDNB confirmed installing using THIS legacy method no longer works from ps4.update.playstation.net and ps4.update.sonycoment.loris-e.llnwd.net via @Sametto Chan on Twitter.
"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."
PS4 6.50 Beta / New Features
From Pastebin.com following the previous developer build strings:
Code:
release: 0x06503010
build: cex
security-repository-path: release_branches/release_06.500
security-revision: 9852
sys-repository-path: release_branches/release_06.500
sys-revision: 117453
***-internal-build-number: 110553
middleware-repository-path: release_branches/release_06.500
middleware-revision: 20512
middleware-build-number: 70689
vsh-repository-path: release_branches/release_06.500
vsh-revision: 172011
vsh-build-number: 1120522