It isn't coming out on October 12, 2010.
A couple of signs against it coming out are:
1) PTR is still up, AFAIK
2) I haven't seen any indication that the arena season is ending this week. Blizzard only said that the season could end as early as October 12th, but they usually give a firm one week warning.
3) There are still far too many bugs on PTR for the patch to be ready for release.
4) There is no good reason to release the patch this week.
5) The patch would be best released after Blizzcon so the Blizzard staff can focus their efforts on the convention, and not be worried about all of the possible things that could go wrong with the patch mere days before BlizzCon.
It's not going to happy, folks. It just isn't.