When you get close enough to the sail date, you will be able to see the details in the app. When the app opens, right above the Daily Planner / My Calendar links, there will be a little rectangle that you can click to get info. It's not populated yet for my September cruise (the box is there, but clicking it just says "Come back closer to your cruise"), but it was definitely there a good month ahead of time for our last cruise.
In the meantime, you can get a good guess from what current 7-night Harmony cruises are doing. If it's the same as Allure, then our order was:
- 2 Formal
- 3 Colorful '70s
- 4 Caribbean
- 5 White Night
- 6 Dress to Impress (lobster night)
ETA: Ohhh, you are talking about menus and not themes, aren't you? Doh! Those you will be able to see under Dining in the app. I can actually already see them for my September sailing: French night, Italian, Caribbean, Mexican, and Royal (lobster). This matches what we had in May for the same ship...