I guess we can say one thing about it. You will probably be able to fly on them for at least 20 years. 727 production ended in 1984 and you can still find one here or there to fly on.
It really comes as a surprise to me. I figured at least another 10 years in production. I heard them say one time on a 777 tv show that I saw, that Boeing expected to have a 50 year production cycle for the 777.