"if Google cares that much about encryption and their users' privacy, they should show me they are willing to implement OTR, ZRTP and PGP" That would only make

"if Google cares that much about encryption and their users' privacy, they should show me they are willing to implement OTR, ZRTP and PGP" That would only make sense if they wouldn't be required to become your key escrow service (=custodians of your private keys). PGP is also a pretty bad choice for private communication, as it offers no forward-secrecy. Something like client-side OTR implementation would be better.