All new features are paid for as content upgrades currently are.
If you overhaul your code you release it first as a free demo (old language; beta), then discontinue it as you release a feature-matched-update to the single paid for version you maintain.
This reduces new features to an individual cost upgrade and ensures your existing users aren't left with an unsupported version.
This is actually a very good result for the consumer. (I'm thinking premium applications such as Audio, Photoshop etc.)
All new features are paid for as content upgrades currently are.
If you overhaul your code you release it first as a free demo (old language; beta), then discontinue it as you release a feature-matched-update to the single paid for version you maintain.
This reduces new features to an individual cost upgrade and ensures your existing users aren't left with an unsupported version.
This is actually a very good result for the consumer. (I'm thinking premium applications such as Audio, Photoshop etc.)