Chrome is doing something similar, deprecating for all but select few exception extensions ahead of v3 rollout. Google's doc with details: https://www.chromium.org/Home/chromium-security/extension-content-script-fetches
Bug 1578405 Comment 1 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Chrome is doing something similar, deprecating for all but select few whitelisted extensions ahead of v3 rollout. Google's doc with details: https://www.chromium.org/Home/chromium-security/extension-content-script-fetches