My understanding is that Star Wars is an extra...everything else will be as is but the Star Wars day will be added in. Nothing will be taken away; at least this is what I was told the two separate times I asked. (Although, technically, what is taken away is a port. Western cruises usually have 3 ports but ours will have 2 and then the Star Wars day.)
From looking at the overview I am thinking that Day 2 will be formal night, Day 3 is Cozumel, Day 4 is Grand Cayman and Pirate Night (with the deck parties but no fireworks), Day 5 is Star Wars day (deck party with fireworks), Day 6 Semi Formal night and Day 7
Castaway Cay. I have nothing official stating any of that, it is just my deduction from looking at the cruise activity overview.