There is a new discussion group for those actively porting the Android platform and/or tools to 64-bit architectures:
It is a non-domain group, and there should be no posting of confidential information.
However, it is members-only, with the membership criteria being approximately
"Are you actively porting Android platform and/or tools to 64-bit architectures?"
It is not for discussion of 64-bit apps at this time.
This is a good time to review the scope of android-contrib:
making source code contributions to AOSP
For contributions related to 64-bit please use the new android-64 instead.