Depends, how long have you been on HRT?
Be forewarned, doing breast augmentation before about the 2-3 year mark on hormones, and you might be surprised with a late growth spurt that messes with them.
FFS, there's not as much harm in doing early, but I'd still wait until maybe 1.5-2 years on hormones before you go changing things that might work themselves out and end up being a non-issue once the 'mones have done their work.
If you have been on them for that long already, then really it's just a matter of what you feel comfortable with socially. If you're still not out to many people, well, it's going to be a lot harder to hide what you're doing afterward, so just make sure you have a solid plan to tell people if they question.