I'm pretty sure that when people are asking about senior year grades dropping they are asking because they were appointed but they might have slacked off the last year once they found out.
Unless you're a re-applicant I'm not sure how they academy will be able to see too much of your senior transcript. You could send the first half of your senior year to the academy right before the application deadline, but then you are trading off an early application that signifies a more motivated candidate for showing half of a year of a transcript.
Now if your grades truly were dreadful, then only you can make the decision on what your path will be during the application. Most candidates will not have their senior transcript when they submit/finish their application, and 7th semester transcripts may be requested at a later time by the academy or sent in by you/your school.
The best thing you could take out of this is something to say for your interview. I know a person who was applying to the academy who had a terrible start freshman year, getting C's in classes like PE and Art. He then improved sophomore year, and pulled his grades up. He used that experience as material during interviews and essays, saying he had the motivation to improve himself once he saw that he was not on the right track. He ended up not getting into USNA but instead USMMA. (He got a nomination to USNA but not an appointment).
Obviously, try your hardest senior year and make the most out of it. Realize that those first 3 years are now out of your control and the opinion of the admissions office on your situation is also out of your control. Try your hardest to make the best application you can, as that is really the only thing in your control.