Ok this might not be the final RTM they could still make a new build and change 16384 to 16385 this could happen due to a last min bug fix. However if all goes to plan this will be the final build.
WinJS 2.0 file from build & Screenshot:
Microsoft OEM news from Microsoft: (1st September OEM Date.)
Paul Thurrott's Twitter Post: (trusted source) MSDN subs might get it earlyer than expected!
Source: MDL Forums.
Expect a flood of news within the next 24hs and possibly a leak. As stated in that e-mail when OEM's get 8.1 they can release it right away if they wish. So if it does not leak by 1st Sep, it will on the 1st.