You don’t have to repot it now, as long as it drains well. In my experience, nursery rhododendron-type azaleas are very tolerant of simultaneous reduction of the branches and the root mass. Once the blossoms drop, I will be pruning away extraneous branches that will obviously not be part of the eventual design, and getting as close as I can to the general shape and profile that the tree has to offer. I’ll also reduce the root mass enough to get the tree into a plastic grow pot. Personally I don’t obsess about getting rid of all the nursery soil. Instead, I cut the root mass down to fit the grow pot with about one finger-width of room on all sides. I then rinse off what soil I can easily remove, and put the tree in the pot with small-particle kanuma all around. I try to get this done before the solstice, so that the tree has time to settle in and grow some more roots and foliage before the end of autumn. My success rate thus far has been pretty good. Right now I have Karen and Rosebud blooming, and Gerard’s Pleasant White about to do likewise. I have several of the “lights” series of rhododendrons [Mandarin, Northern, Lemon, etc.] leafed out and with blossom buds swelling.