Well judging from the Magical Adventure, i also read somewhere i think midway or before, one of the episodes, talks bout their marriage ceremony, i'll put it in quotes. "It is rumored the wedding ceremony for Bloom and Sky may possibly be planned out and the wedding dress will be picked out. This will happen in the Magical Union and the Domino Ceremony." Can't wait..
Yup just rewatched magical adventure, to anyone who didn't, please do. The ending will prove useful for everything in season 5, all the matter of waiting till the wedding episode :)