Decline for and reapply next year?
I would wait until you know the outcome first. It is possible (and not that usual from what I hear) to defer an offer of admission, which means you may be able to take up an offered position in the following academic year.

Since you do not know that you have been admitted yet, I would wait until you get a response. If you are rejected, there is no harm in re-applying next year. If you are offered a place, a request for deferral will not be looked upon badly.