This is a huge problem that's akin to "replacing HTML/JS." It's a non backward-compatible change that make the plugin nearly 100% useless for current PGP users. Obviously folks can generate new EC keys, but they will be reluctant to abandon keys they've had for years that contain valuable third-party signatures. I think this will be a huge hindrance to adoption, and it would be imperative for the community to implement RSA, even if it's only for key import and interop, not generation.