I think it is next to impossible to view 50 years in the future, but I can try to make some predictions.
-I hope that supersonic sub-orbital craft will at least start revolutionizing air travel by 2050. You could fly to anywhere in the world within 2 hours. The basic technology for this exists, but can they make it cost effective?
-Superjumbos will be around with the A3XX making its appearance sometime next decade. Boeing may respond years later with MD's Blended Wing Body aircraft that can carry 800 and is a revolutionary design that should be credited to solely to MD.
-I sincerely hope that we won't see another generation of 737's. It would be suicidal for Boeing to do that. They need something more revolutionary like their 7J7 project to become a reality. Boeing cannot survive in the narrowbody market by passing off more derivatives, they are already suffering in my opinion.