Yes, I think so, because otherwise the Church would have made a declaration in canon law stating that plenary indulgences cannot be obtained during the interregnum, or the vacancy of the Holy See. Such an indication does not exist. So we have to conclude that people can nevertheless gain a plenary indulgence simply by praying for the Holy Church. That is the intention and the Pope.
However, I think that in the future, perhaps a Pope could reformulate this condition. This is only my idea: instead of requiring a prayer for the intention of the Pope, it could be for the intention of the Roman Church, since the Pope is the Bishop of Rome.
In the Roman Missal, there is a short expression of intention that the priest can formulate before celebrating Mass. It is optional and says: "I will celebrate this Mass for the greater glory of the Holy Trinity, for the Church Triumphant, for the Church in Purgatory, and also for the Church Militant, especially for the happy state of the Roman Church." Such a formulation exists in the Roman Missal and, perhaps in the future, instead of praying for the intentions of the Pope, it could simply be for the spiritual well-being of the Roman Church.
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