 (1′) is dubiously true, at best. It might well be that Lorenzo Valla will overtake Petrarch at some future time, being a famous humanist more closely associated with the Italian Renaissance than Petrarch. And Valla did not write the epic Africa. On the other hand, (2′) is true, at least assuming, for the sake of an illustration, that (1) and (2) are true. On that assumption, it does not matter that Valla might overtake Petrarch later: that will be too late to affect their respective status as it is now.