In less than 4 days you'll be able to try it. The new iOS versions are normally publicly released during or just after the September special presentation.
Oh I have a Dev account and I could download it now, but I choose to keep 10.3.3 on my 7 Plus. I won't see the iPhone or watch new OS until I get the new iPhone and new Apple watch. It's by choice. I will be keeping my 7 Plus as a backup.