This is what the Holy Father means when he invites other to become saints; it has nothing to do with becoming a "professional saint", whatever that is. Saint = one who is holy ("sanctus"). It is not an office in the Church or any special recognition. Indeed, most saints are known only by God. Which is why we have the Feast of All Saints.
Neither we nor the Pope can't invite anyone to holiness. Only God can do that. It would have been a lot more "patristic" of him to say to be prepared to answer the call, whatever it may be, and to submit in perfect obedience to God's will. Let God decide who will be a saint. A little humility can go a long way.