Not just no, but Hell No!
The new films are going to have a hard enough time overcoming the ill will that the prequels created. No way should they actually insert actual PT remnants into the ST.
Ewan McGregor did a pretty good Alec Guinness impression in the PT (so I can't fault him for that), but there's no need to go inserting him into the newer films.
And Hayden Christensen...really?...REALLY?!!!