You're operating under the assumption that if this is turned on by default in the future, everything will go to CloudFlare.
While CloudFlare is being used for the opt-in study, you have no evidence that they will be used in any on-by-default scenario. Nor do you have any evidence that only a single DoH provider will be used globally.
While CloudFlare is being used for the opt-in study, you have no evidence that they will be used in any on-by-default scenario. Nor do you have any evidence that only a single DoH provider will be used globally.
Perhaps you should monitor Mozilla mailing lists.