I don't have a definite answer. There's the path we're executing on at Open Whisper Systems, but there are a bunch of other projects working in this area as well (Mailpile, LEAP, etc).
I think the problems are solvable, but only if we have a different design approach. So when I see projects trying not-PGP, I'm interested. When I see projects building on PGP, I'm less interested.