Considering the age difference, I doubt PSG or Barcelona would be interested in a swap deal. Author and Veratti are 23 and 27 respectively, and are both mainstays at their clubs. Pjanic (30 years) is good fit at either club but a swap deal is unlikely to happen, the player however seems keen on a move to Barcelona, one of the names that have been rumoured to be open to a swap deal is Jean-Clair Tobido who is currently on loan from Barcelona at Schalke.
Teams will do a lot of swap on the next 2 markets sessions with overvaluations of players and no money spent.
This is the only way they have to generate fake money to be safe for the Financial Fair Play and the COVID crisis.
For example Juve and Barca could swap those 2 players for 60m and both teams will be happy signing a +50m € for the Financial Fair Play.
To me on these sessions we will see a lot, A LOT of these exchanges.