it will double its size in flowering or even triple, the reason why your plant is so tall is because its stretching too much for the light, but in the 2nd pic i can see it starting to bush out which is good, those 2 new tops that are growing now will get big in flowering, possibly even bigger then the plant itself which is what mine has done
EDIT: the bad thing about plants stretching is you get a tall plant with a thin/weak stem, which can make it unstable and you might have to tie it to a support pole just to get it to stay upright when do you start flowering