Pesci got jerked around on the original deal for this movie that years ago before Cannes. As well as the Travolta/Gotti movie that hasn't yet panned out. He sued on the Gotti movie and won like 3 million b/c he had to gain weight and they never got the ball rolling in the film.

He did The Good Shepard, that CIA/Cold War spy thriller in '06 where he plays a fictitious version of Carlos Marcello. He also did that brothel true story, Love Ranch in '11 I believe but as of now he is closer to fully retired than semi-retired from film. If The Irishman being green-lite isn't worth it for him, surely he's happier away from acting, maybe it's for the best and somebody else steals the role in memorable fashion.
I believe Pesci was to be casted as Bufalino, that could become a very classic character if done correctly, I'm very interested to see who is cast instead in what could be the role of the film in all likelihood, depending on which themes of the book the film decides to adapt.