Also, he didn't leave acting until 6 years after his wife died and he isn't fully retired. He's done some stuff and has been quoted as saying if he liked the new script he may do it.
“I haven’t talked to Dan Aykroyd about it. Somebody he’s associated with called me and I said, ‘I wouldn’t not do it, but it’s got to be good.’ You know, I’m not interested in doing anything I’ve already done, and I thought the second one was a disappointment. But I guess I’m interested in where that guy is now. I sort of see him as being Bernie Madoff’s cellmate in jail. Both of them being so orderly that they race to get up and make their beds.”