The 64 bit chips are starting to arrive.

Applied Micro Xgene is apparently shipping.

Nvidia K1 is or is soon shipping and getting some pretty stellar geekbench scores.

Mediatech announced the MT6795 8 core A53 / Mali-T760.

Samsung announced the Exynos 7, Quad A57 and quad A53 + Mali-T760.. The international Note 4 has this chip.

Allwinner have a 64 bit chip on the way but don't seem to have said much about it yet.
They do have a dev board on the way:

http://liliputing.com/2014/10/allwinner-nobel64-is-a-64-bit-dev-board.html


In the mean time they'll sell you a $4 quad core A7.

I would have expected 64 bit to appear at the top end and slowly work it's way down.
Look like they'll appear in the mid to low end stuff very rapidly indeed.