At first, they said some time in mid August. During mid August, they said mid September.
It's October and I have yet to play creative mode on Xbox. I just hope it comes out soon.. It's been about 2 months since the last update.
No idea of an exact date yet, but my guess is somewhere between 2-3 weeks.
I'm guessing you're talking about the Xbox Edition, since you mentioned creative mode in it. It'll be out either sometime this week or next week. They sent it in to Microsoft Cert Testing so if they find any bugs, it'll take longer, if not then it will be out sooner.