Just for the record, I have no inside information at all. I am not affiliated with any of the fantastic dev groups around here or on other sites. I just read a lot on here and other sites, not just for our phone but others as well.
That being said, I have said it for awhile that it was gonna be mid-September, I only revised it to go a bit later because of this leak. IT IS NOTHING BUT A HUNCH. No basis of fact at all. No inside information. I do feel strongly about it and if you wanted to make a wager, I would jump on it.
As far as going stock, I wouldnt even when it does come out. My reasoning here is simple. All of the good dev groups have already been making custom roms off the leaks and when they get a final code, I can see Gummy coming out with a solid custom rom within a few weeks. Even if the stock GB is fast, a custom ROM will be worth the extra wait.
Also, we will have more options. CM7 will get done sooner with an Official GB (with LTE enabled). There is another one I know nothing about called darkslidecharged that will be out too. I hear good things but have no experience with them.
I would do whatever you want with you phone and not be shackled with worrying about having to go back.