Im not updating my PS4 but for those of you interested, heres the release notes:

As usual the only 'changelog' entry is: “This system software update improves system performance” and normally that means something has been patched, which @Mathieulh has confirmed the currently available webkit exploit is closed, but no big deal as it was not a kernel one anyway, but it does mean Sony keeping an eye open what is being released out there in the wild.
Firmware 5.53 is now giving you more options to choose how much data you want them to collect from your console. This includes data about online services (which cannot be deactivated), and navigation data (how you use the console. That part can be turned off). In general, my personal recommendation would be to share as little data as possible, independently of your use case.

If you choose to update (which we don’t recommend if you expect to hack your console one day), head over to the settings to reduce the amount of data you share.
As you can see above, the new firmware allows you 'cut down' the amount of 'public data being shared out' which is most likely the main reason for this update as Facebook got into trouble recently with this, but if you looking for 'future hacks' don't upgrade yet!

NEWS SOURCE: PS4 Firmware 5.53 has been released (via) Wololo