Should Mark retire? Short answer. NO.
You are talking about one of the greatest guitarists and songwriters of all time!! He has been a huge influence on the art of songwriting and guitar playing, he has got more prolific as he gets older, he can do everything, sing, write lyrics, compose music, play guitar, he is quite simply one of the greatest musical artists the world has ever known!!! He doesn't have to do it, but he loves to do it, it's a compulsion with him, it has been his life's work. The day Mark stops making music will be a very sad day. I remember the likes of Hank Marvin and Mike Oldfield saying they had gone into retirement, but they both released new albums this year, I think if you reach the level people like that do, you never retire. I think as fans we have been spoiled by Mark over the solo years, and long may it continue.