Just recently we saw support for kernel dumping added to VitaDump, and today PlayStation Vita developer St4rk released PKGDecrypt which decrypts and extracts PS Vita Package (PKG) files! 
Download: PkgDecrypt-master.zip / GIT / vitakeys (fixed) / vitatool (fixed) / PKG EXTRACTOR AND PKG TO PKGS CONVERTERv2.zip / MakePKGS.bat / PKG Extractor.zip / PKGExtractorGUI.exe / PkgDecrypt-Frontend via @SilicaAndPina
To quote from the README.md:
PkgDecrypt
Decrypts and extracts PS Vita PKG files
Dependencies
OpenSSL
Thanks
Proxima - Helped me with doubts about PKG Crypto
Some related PlayStation Vita hacking scene articles for those interested:

Download: PkgDecrypt-master.zip / GIT / vitakeys (fixed) / vitatool (fixed) / PKG EXTRACTOR AND PKG TO PKGS CONVERTERv2.zip / MakePKGS.bat / PKG Extractor.zip / PKGExtractorGUI.exe / PkgDecrypt-Frontend via @SilicaAndPina
To quote from the README.md:
PkgDecrypt
Decrypts and extracts PS Vita PKG files
Dependencies
OpenSSL
Thanks
Proxima - Helped me with doubts about PKG Crypto
Some related PlayStation Vita hacking scene articles for those interested:
- Oh My Lanta: PS Vita Scene Groups PSiCO & TRSI on Game Dumps
- Vitamin PS Vita Game Backups Playable as VPKs by Team FreeK!
- Tokyo Xanadu Rumored as First Decrypted PS Vita Game Backup
- Adventure Time is The First PS Vita VPK Backup Game? Not Quite!
- PSA on Cobra BlackFin Device, PS Vita Scene Game Dumps Surface