Most TAs, if you used one, will work to get your reservation price lowered if the price dropped. No need to cancel and rebook. It is easiest before final payment date, but it can be done after.
It's more tricky, but still doable, with the use of an MNVV as those can only be changed once.
As usual, @cantgetin is correct. The new bar tab bonuses began on the 17th. The new FL resident discount is not combinable with MNVV (although the previous ones were). There are still TAsa with stockpiles of the old "good" MNVVs.
As also alluded to, TAs who belong to some large travel consortia can add $100 OBC,even with MNVV use. Applies to around 140 sail dates, but not all. If you have a TA, ask!
The rules change frequently, it is full time work keeping up 🙂