While no official changelog is available yet, according to their announcement the update will offer users the following, to quote: "system software stability during use of some features has been improved."
It wouldn't surprise us if Sony blocked some of the more recent exploits in the update as well, however, it is currently unknown if this will be a mandatory PS Vita Firmware update or not but it should...
1: Patch for all CoreOS Checkoff (the CFW and downgrade console compatible with the PS3 console that does not go to peuve desous
3.56 Now it peuve desorme install version 5.2 in service mode with the mode lv2diag downgrade)
2: Adding icon XMB direct links to the forum teamSGK and version number of cfw (normal and Cdex)