They have not changed the formal nights - I love formal nights. I would say by far the majority of people dress up on those nights. I think it's kind of sad to see those who insist on wearing jeans to formal night - but it doesn't affect my cruise.
formal nights ,most people that go to the main dinning room will be dressed for the occasion. smart casual is not really done anymore, but I personally dress in nice pants and collared shirt every other night. I am with felix, no jeans or ball caps any night.
Other than your 2 "formal" evenings, you can pretty much follow the dress code for casual nights. I wouldn't bother packing a sports jacket, just takes up too much room and you hardly see the guys wearing them, just a nice polo type shirt and docker type pants will do nicely. I understand they are allowing jeans, way to go!