Well, you can lose the weight any time you like. It might be easier to lose muscle once on HRT, but it will be more difficult to lose fat - so, it's up to you.
Anyway, I haven't changed a whole lot. Lost five pounds of muscle or so, gained three pounds of fat, and that's a few months over two years. I was pretty skinny to start out with, always hovering around 100lbs.
Something went right, in any case. If I were to gain 10-20lbs, I might even have a shot at an hourglass figure - beforehand, my body was straighter than William Shatner (har har), so I'm actually pretty surprised. I might as well have not had a waist, and my hips were non-existent.
Fat redistribution will happen, and it might be pretty profound. I'd start losing the muscle if I didn't appreciate it, and I'd work on being slim and toned and fit for HRT.