Great question. The core crypto library in End-To-End has already supported ECDH on Curve25519 and Ed25519 since day one [1]. We're discussing with GnuPG team on extending RFC 6637 to include these algorithms in the OpenPGP standard.
I spent the weekend digging into both End-to-End and OpenPGP.js, and it appears the End-to-End has the primitives for Ed25519, but it doesn't recognize signature packets that use Ed25519. Is there an e2e bug tracking compatibility with GPG 2.1 signatures that use Ed25519?
[1] https://code.google.com/p/end-to-end/source/browse/javascrip....