I think Pope John Paul II could speak even more, 12 I think.
Pope Benedict XVI also spoke several, though I'm not sure how many.
And all of them would have known Latin, Hebrew and Biblical Greek.
I think once you have studied those languages and a couple of foreign languages it becomes easier just to keep adding more because you have the knowledge of how to learn effectively, grammatical structures, roots of words etc.
I know a priest who arrived in the country I am living in with no knowledge of the language but fluent in 5 other languages. Within 3 weeks he could hold a conversation in the new language and within 2 months he was completely fluent and preaching.