Considering the fact the two have been in the industry and such a big part of Bollywood (wrt production, playback singing and doing versatile stuff), they haven't ever been paired.
However, if a report in Mid-Day is to be believed, Priyanka will essay the role of Aamir Khan's wife in a particular biopic. Earlier there were reports of Aamir romancing on-screen daughter Fatima Sana Shaikh in the biopic, but recent rumor mills suggest that Desi Girl might be the one pulling off this role.
And this pairing has got us excited. If things go as planned, it is for the first tome that Priyanka and Aamir will collaborate for a film.