No one can predcit seas conditons several months ahead but last year they were not calm with several days of rough weather. The average age of cruising is dropping but not so much on Cunard as others so yes there will be a good number of plus 60's on board.
As Bill says, no one can accurately predict the weather and I experienced really rough seas last October and great weather the october before and this year could be different again. By the same token no one can predict how other passengers will react or relate to you as we don't know you. I will say that most passengers do not think of age when they are forming friendships onboard it's done mainly on personalities.... Neil.